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Come Out of the Bloody Cold: The Case for Neoprene with O’Three founder Sean Webb



By Michael Menduno. Images courtesy of Sean Webb unless noted.

There is arguably some confusion in the tech diving community over the advantages and disadvantages of neoprene suits versus the perceived virtues of trilaminates. Accordingly, InDEPTH chief Michael Menduno conducts a deep dive into the case for neoprene with head neo-advocate Sean Webb, founder and president of veteran British suit maker O3. The pair even take a short excursion into hydrogen diving with an O3 ambassador—the Wet Mules’ Dirty Harry. Are you feeling lucky today Punk?

It’s not an exaggeration to say that Sean Webb has been working to keep divers warm for nearly 40 years. The 56-year-old, water baby turned diving business veteran made his first scuba dive at age nine when his father helped him strap on a 10-liter aqualung and attached a rope tether to restrict his depth to two meters/six feet. Webb was hooked. Six years, two dive clubs and numerous dives later, he earned his ocean diver certification at the BSAC’s Weymouth Dorset Club. 

The next year, Webb followed his dreams and joined Ron and Joy Parry’s family dive business, SubAquatics, which they had founded in the 50s, in order to make neoprene wetsuits and drysuits. The teenage waterman never looked back. In 1989, when the family business dissolved, Webb decided to stick with what he knew and formed O’Three. He was later joined by one of the Parry sons. The name is derived from the chemical symbol of ozone, O3, which was one of the big environmental issues of that time.

Webb is surrounded by water on the limestone-tied island of Portland on the UK’s Dorset coast—the Jurassic Coast as it is known—which has been designated a United Nations World Heritage Site. Here, the boutique British drysuit maker quietly built a following and a reputation for making dry, warm, high quality neoprene drysuits that has continued on to this day, some 33 years later—no small feat for a diving business! In recent years, O’Three added wetsuits, and most recently a trilaminate suit in response to market pressure.

O’Three’s ambassadors and friends include Australia’s Wet Mules, who are conducting some extraordinary exploration, and knighted British diver Sir Rick Stanton of Thai cave rescue fame. Then there’s dive training veteran and RAID vice president Steve Lewis, the training officer for the Somerset Section of the British Cave Diving Group Michael Thomas, and YouTube influencer “Adventures With Purpose” principal Jared Leisek, to name a few. 

Full disclosure: I am an ambassador as well, and own an O’Three Ri-2 100 neoprene drysuit. I am also a Fourth Element ambassador and dive an Argonaut 2.0 trilaminate suit. You could say I’m a bit of a Anglophile, when it comes to dry suits—they dive cold waters. In addition, I own an older DUI FLX Extreme, made in the USA. 

Webb and I have been having informal ongoing discussions about neoprene for several years. It’s a subject that is not well understood by many divers. So I thought I’d reach out to this veteran pundit of polymers and ask him to make his case. Here’s what the man had to say.

By my count, you have been in the diving industry for close to 40 years, and you always seem enthusiastic and positive. Where do you find your inspiration?

Ha! I was just speaking to one of the guys who does a lot of graphic design for us. We are not a fashion brand, but we are coming up with a new range of T-shirts. I said to him, “Dave, we really need to tap into where we live. California is a great example. There are so many great brands that are tapped into California and the lifestyle. But we live in an incredible part of the world here in Dorset. We live on the Jurassic Coast and are surrounded by seawater. 

The Jurassic Coast

I think that’s what inspires me; it’s the environment here that helps us design the suits the way we do. If our suits can put up with the rigors of the Dorset Coast and the weather that we have here, then we are going to be making some pretty decent suits. That’s what drives us. You can’t help but be inspired every day when you wake up and traverse the causeway to come to work. We are very lucky where we are.

I’m going to have to come and visit you next time I’m in the UK for sure.

There’s phenomenal diving. I guarantee you! 

Sean Webb in the loop

Before we get into drysuits, I’d like to know what you think the biggest changes are that you’ve seen in the industry over the last 40 years? 

Obviously, rebreathers have been the big change, although they got off to a slow start. I think they’ve revolutionized scuba. It’s been phenomenal. To see people getting into diving and going straight into rebreathers. Ten years ago, people didn’t think that would happen, and now it has. Of course, the continued commercialization of what was predominantly a recreational pastime has been going on the whole time. Has that been good for diving? I don’t know, but the move to rebreathers has been incredible.

Craig Challen of Wet Mules fame

It has. You know, judging from today, when we look back at the “Technical Diving Revolution” that emerged in the late 1980s/early 90s, you could argue it was really all about moving to rebreathers. It has just taken us a while to get here. As a community we first needed to develop and create the infrastructure for mixed gas diving, as a necessary step.

Let me ask you the same question about drysuits. What do you think have been the biggest developments in drysuit technology over the last 30-plus years since you started O’Three? 

One word: neoprene! I think a lot of individuals are stuck in the Dark Ages and think that when it comes to neoprene, we’re still dealing with a fairly thick robust material that was invented back in 1930 and hasn’t changed since then. Whereas the truth is that neoprene compounds have gotten better and better and manufacturers have gotten better at making thin neoprene drysuits that stay dry for long periods of time.

 When we first started it was a 7 mm, or maybe a 5 mm drysuit if you were pushing the boundaries. Whereas now, we can produce a 1 to 2 mm suit that’s strong and robust and divers have a great time in them. Without a doubt, the biggest change has been the neoprene.

Neoprene rules!

Ha! I was thinking you were going to say front zips, dry gloves and P-valves.

Yes, all great developments, especially now that dives run into hours rather than minutes. But if you’re not DRY and comfortable, you’ll not be in the water long enough to warrant using dry gloves or a P-Valve. As for front entry zips, they create as many issues as they solve. But that’s a subject for another day.

We’ve talked about neoprene before. Obviously, there are a lot of new divers who get exposed to neoprene for the first time with their wetsuits. But for many, that’s it. Most tech divers upgrade to a drysuit and go straight to a trilaminate without ever working with neoprene. What should divers understand about neoprene that maybe they don’t?

Whether it’s neoprene or trilaminate, we always say that we spend as much time talking about the under suit, the base layers, the thermal layers, whatever you want to call them, as much as we do the suit. If you get that combination wrong, for example, you get your neoprene drysuit but your under suit combination is wrong, you could have a nightmare combination. 

It’s the same if you get it wrong with a trilaminate. 

So, we tell people: don’t think neoprene is the devil. If you wear the right under suit, which means you wear a much thinner under suit, you can have a terrific time in a neoprene suit and be better insulated, because the neoprene gives you that installation with a much thinner base layer. 

What that means for most people is that the buoyancy change, which takes into account that both the drysuit and the under suit, is minimal. Yes, there is a little buoyancy change in the neoprene drysuit but very little buoyancy changes in the under suit. And people tend to forget that. Whereas with a trilaminate, you’ve got no buoyancy change in the trilaminate but a huge variation in buoyancy in the under suit as it compresses, because it’s that much thicker.

The air, err gas, in the under suit compresses.

Right, it’s the combination of the two—whether it’s shared between the neoprene and the under suit—or the trilaminate and a much bigger under suit. So labeling neoprene the devil, and trilaminate utopia, is simply misleading. I think you’ve experienced that.

I have. I own an O’Three 2.5 mm neoprene suit, of course, and two trliams and have come to appreciate that it’s the combined system when you’re talking buoyancy. Even though people buy the argument that neoprene is a great insulator, they have in their heads that it compresses at depth, and so they get no insulation at depth, and it will screw up their buoyancy. Which isn’t true with the new materials, correct? 

No, it isn’t true. We’ve had some interesting conversations about this, even with the likes of some of our military users who should know better. If the suit starts off at 3 mm and it goes down to 0.5 mm, you’ve still got some insulation there. Whereas with the trilaminate suit, at the surface, at 30 or 40 m, there is zero insulation. It just keeps you dry. 

Of course, the neoprene expands again during ascent, and again, people think it’s going to send them into a tailspin and they’ll come accelerating to the surface. But if you’ve done your buoyancy checks, there shouldn’t be any issues. The neoprene is going to expand at 10 meters and shallower just where you are going to need that extra bit of insulation for the long part of your hang. 

I know you make several sizes of neoprene. I want to ask you about them: the Ri 100 (1 mm), Ri 2-100 (2.5 mm) and the MSF 500 (5mm). But first, I noticed on the website that the Ri 100 isn’t there anymore. That’s the crushed neoprene, right? You have discontinued the line?

The short answer is, yes we have. And credit where credit is due; that suit was inspired by DUI (Diving Unlimited International) and the materials that they made many, many years ago.

Yup, I used to have a CF200 back in the 1990s. That was “The Tech Drysuit” of the day and the team at Capt. Billy Dean’s Key West Diver all had them. DUI still makes them, but I believe they use a different neoprene these days.

The author sporting DUI’s CF-100 crushed neoprene suit circa 1992. Photo by Bret Gilliam

Exactly, credit where credit is due. I’m not going to get into any politics there, but crushed neoprene is not the material that it once was. And our RI 100 material was brilliant. When it was on point, and our manufacturer was ticking all the boxes, it was great. But to make that material requires too many processes, and there are a host of variables. As a result, the tolerances that we were getting made it difficult, if not impossible, to manage and work with. We decided to put it on the back burner. Ironically, we replaced it with a trilaminate suit, which may seem odd, as we have a long history as a neoprene manufacturer. 

I want to talk about your new trilaminate suits, but first I have a few more questions about your neoprene suits. What is the difference between the Ri-2 100 (2.5 mm) and the MSF 500 (5 mm) in terms of diving characteristics? Obviously, it’s thicker neoprene, but what does that mean operationally from a diver point of view?

The 5 mm neoprene suit has been our bread and butter. Think of it as a modern version of the good old-fashioned 8 mm suits, which were great in their way, but things have moved on. You’ve still got a nice piece of neoprene wrapped around you. It can fit a little bit better because the neoprene is the thing that’s giving you the insulation. You only need some very thin base layers underneath it. Nothing big and bulky. And people, shall we say from a more traditional neoprene background, will like that type of fit and feel. Again, because the insulation is in the neoprene, we can cut it slightly closer, err tighter. 

The result is that because it’s fitted better and only needs a thinner base layer, the buoyancy variation of the 500 is likely less than that of a loose fitting trilaminate with really thick under suits. It’s more streamlined, so you’re pushing less bulk through the water. It does change at depth. It will lose its thickness at 30-odd meters. It will be half the thickness. But again, if you’ve done your buoyancy checks and you’ve got that nailed, it shouldn’t be an issue. 


The fact is, over the last 33 years, you’d be surprised by the number of people who’ve come to us and said, “Do you know what? I’m wearing less lead with the 500 than I was with my big trilaminate and under suit which was bulky underwater.” They’re wearing less lead with it. The proof is in the pudding, you know? 

What about the 2.5 mm suit?

It’s a completely different rubber compound, so it compresses much less. It is going to be colder because it’s not five mil, but you have to put a thicker under suit on underneath it, and you make up that difference in the insulation. It’s a nice combination between under suit and neoprene, and you share the responsibility of the insulation between the two elements of your drysuit. 

In the warmer months, for people who still want to wear a drysuit, we sell a lot of those to people who dive and instruct in the Red Sea, and they’ll have a two point five mil neoprene. It’s not so onerous when it’s a little bit warmer. They’ll wear some Lycra leggings underneath it and a T-shirt and carry on diving and then throw maybe a slightly thicker under suit under it. In the winter, they will bring it back to the UK and dive with the appropriate undersuit. It’s a bit more versatile across a wider range of temperatures.

My first drysuit, back in the day, was an SAS neoprene suit with a back zip and all neoprene seals. Remember those? I loved it compared to a wetsuit. OMG! California has cold water. I forget if it was a five or an eight mil. It was probably an eight. Because it was old and that was what people did back then.

We are still making the odd eight mil neoprene drysuit today. And we still make a 7-8 mil hood-attached jacket and long john or farmer john for commercial scallop divers. They love it. They love that feel of a wetsuit. Okay, they’re not diving in January and February in the UK, but…

Come out of the cold! Brrr

Do new UK divers go to drysuits right away? Is that pretty typical?

It’s becoming more typical. I’d say it’s probably 50-50. But I’ve got no statistics to back that up. Again, 10 years ago there was definitely, “get yourself into a wetsuit or a semi drysuit, get a year under your belt and then get a drysuit.” But I would say there’s definitely more push to go straight into a drysuit. And why not? If you’re taught properly and you understand things, then great. 

I’m still a bit old school and would rather see people dive for a year or so in a wetsuit to just focus on their skills rather than have to worry about a drysuit. Because they can bite you in the bum if you drive them wrong. Fine-tune all your skills and then jump into a drysuit.

That makes good sense. Over the last five years, O’Three has added trilaminate suits to their product line. What was your motivation?

First and foremost, we don’t necessarily always make decisions on the best business practices, because we’re passionate about it. I’m not going to pull any punches; it was a business decision. Neoprene can’t be everything to everybody. We came back from DEMA after listening to many of your fellow tech compatriots saying, “Do you make a lightweight front entry trilaminate?” 

After saying “no” to a not-insignificant number of people, we came back on the plane and, after a few whiskeys, said, “We’ve got to master this trilaminate.” And that’s what we did. 

Video by O’Three

It’s been really successful. We didn’t run before we could walk. We knew about trilaminate, but we’d never put one together until four to five years ago. It’s been an interesting journey. In fact, we are just about to expand the product line—the production facilities here at our base in Portland, Dorset. It gives us another bite of the cherry, or slice of the pie, so to speak, and they are backed up with the same customer care and product detail and attention to detail that we’ve done with the neoprene. People are starting to respond positively.

Have you done anything special with them? Anything unique to O’Three?

We can offer many customizations. Gear and suits can’t be all things to everybody, but we can offer many options. In order to attach neoprene seals directly to the suit, a lot of people are moving to ring systems, which we can do as well. We tried to keep the front of the suit fairly clutter free, so we haven’t double-zipped the front entry. We offer an Aquaseal YKK plastic zip running across the front or the BDM medium duty metal zip running across the front, and we’ve come up with a nice clean way of covering the zipper and protecting it without applying another zipper over the top of it. Generally, that is A: a bit of a ball ache to the manufacturer, and B: When they do break, because they will break, they are very difficult to replace. So, we just kept that nice and clean and clutter free.

The O’Three Trilaminate Line

Sounds well thought out. I will take a look at your trilaminate at DEMA this year in Orlando. Will O’Three be coming to DEMA?

To be honest, we’re having a good time selling suits directly to the people in the US. The days of going through a distributor are gone, we feel, and DEMA is quite expensive, as you know. So, the jury is out yet as to whether we are going to be there. We do have a nice following over in the U.S. A couple of years ago, we added an influencer named Jared Leisek, who hosts “Adventures with Purpose,” and that’s really boosted our reach. 

It’s been quite a revelation for our business that had relied on all the traditional ways of advertising and word-of-mouth. So that’s been very, very interesting. He’s coming up with some good results.

O’Three HQ

What would you say is O’Three’s key differentiator, err secret sauce. Is there something that you feel like, “this is our core that we do better than anyone else”?

I’m sitting here and not really racking my brains because I’ve got the answer. I think the main thing with a company like ours is that drysuits are 98% of our business, and if we don’t get it right, we don’t have a business. So all of our focus and all of our energy is on making sure that we make the best possible suit we can. And if things do go wrong, and they do for every company at some point, we’ve got to give people five-star service. If the shit does hit the fan, we’ll move heaven and earth to put things right for people. I think those two things are what sets us apart.

That makes good sense. I see on your website that you stress quality and customer service as your key focus. I know for me; my Ri 2-100 feels like a Mercedes or a Porsche—the quality is just evident. But of course, everyone says, ‘Yes, we make a quality product,’ but what does that actually mean when you say we make a quality drysuit? Talk to me a little about that. 

Again, I think you have to look beyond what’s staring you in the face, which is a sheet of neoprene or a sheet of trilaminate material and some glue and some tape. We’re always thinking about the end-user and how would we want to be treated? What sort of product would we want to buy? And I think that drives us when we’re putting things together.

We do a lot of manufacturing here in the UK. The entire trilaminate line is made here. We have manufactured in the Far East for many, many years, and though other vendors do as well, there are definitely differences.

That’s in the specification, and the fact that we go to the factory during every production period. So, perhaps it’s just a little bit more attention to detail. We are not making units for anonymous users. We slow things down. 

Commercial divers favour neoprene suits .

Putting a wetsuit together is fairly easy, but when you’re talking about drysuits, if the seam is not spot-on from start to finish, we’re going to have failures. Maybe not when we initially leak test it, but six months down the road we’re going to have failures. And so, we need to give that attention throughout the early stages. For us, the tape on the inside of a suit is just there as an insurance policy. It’s not an integral part of making sure that the suit stays dry—that’s been done before we put the tape on. Make sense?

“What sort of product would we want to buy?” Yes. I can totally relate to what you said from my experience making aquaCORPS back in the day, and now InDepth. What sort of story do I want to read!

Let me ask you about neoprene, because as you have alluded to, all neoprene is not the same, right? There are grades of neoprene, levels of quality. 

Exactly. The market starts at the very, very bottom, with neoprene products in Walmart and discount stores; the neoprene is neoprene in name, but there’s very, very little neoprene in it. It’s a mass-produced material that won’t stand up to UV or to compression. It’s great on the surface, but the minute that you put it under water, that is under pressure, it’s a different ballgame. 

It’s important to make sure that the neoprene compound that’s being used reflects that. The surfing industry has been a major driver of neoprene technology. There are many more people surfing and doing surface water sports than diving, and for them compressibility is not an important issue.

When we speak to neoprene manufacturers, we say it has to be a dive-grade neoprene. And there are different grades within that genre as well. You have to choose carefully and make sure that you use certain neoprene on different areas of the body. For example, the Ri 2-100 uses four different neoprene compounds. The nylon linings have an impact as well. There’s more to it than meets the eye.

I know you have quite a few ambassadors. The Wet Mules are one. That’s a group that I follow and they’re doing some amazing diving as you know in Pierce Resurgence and other places. Rick Stanton is another, right?

Rick Stanton has been a customer and a friend for years and years. He quietly does his thing, as you know. Obviously, he’s getting some international recognition now, and I think Ron Howard’s film, Thirteen Lives, is coming out in November. So that’s going to put him and the rest of the guys on another pedestal, and quite rightly so. But he’s one of those people that just gets on with it quietly. As does John [Volanthen]. [Ed note: author of Thirteen Lessons that Saved Thirteen Lives]. John was in the shop last week. They never expect anything and are always happy to pay. And we have to tell them, you’re not paying. They are such great unassuming guys. 

They’re heroes in my book.

They are phenomenal.

Aquanaut Sir Rick Stanton in his 4mm O’Three

I have another technology question. I was just up in British Columbia and I noticed that all the locals up there, or at least most of them, were diving “heat”—electric heating systems. Many used the SANTI system, and there was another company called Versatile Technology that makes a vest with batteries. What are your thoughts on electric heat?

It’s a bit like the Ri 100. We made a heated under vest many years ago. Again, cutting to the chase, we stopped doing it about four years ago because the market was so small back then. SANTI is doing a great job BTW. I would say that they’re probably the market leader.

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It seems like, yeah. DUI had a product for a while, Blue Heat, but they withdrew it. I don’t think they offer that anymore. 

It’s such a small niche market. We’re still making our heated vests for the British Special Boat Service (SBS). And we’ve had that contract with those guys for 20 years now, nearly. But the general public, being diplomatic now, just don’t apply the same level of care. It was a difficult product to support because of electricity and water. There’s a lot that could go wrong, and you do need to look after it. So, we decided it’s not our bread and butter, and we decided to leave that to the bigger boys. SANTI is there. 

Irish Army Ranger Wing diver packing their O’Three.

Of course, heat is not just for tech divers but anyone diving in really cold, single-digit water, right?

Going back to the basics: If your drysuit and under suit are really dry, it’s much easier for your body to heat up the dry air. So, if you have that right and you’re still cold, then perhaps you should look at a heated suit. Because, dives are often more than an hour. It can be two, three, four hours. The Pierce Resurgence guys [aka Wet Mules], bloody hell, they’re in the water for 15 hours.

Yeah, in 6°C water. Oh my God. You make heated under suits for them, right?

Yes, some of the Mules are using them, and some are using their own iterations of systems that are out there. They’ve got to bring anything they can. 

Our heated under vest is a loom of wire, and the switch went through the inlet valve. We adapted a standard APEX non-swivel valve, and then we put the on-off switch there. The battery pack is attached outside of the suit. But I believe the Mules also have battery systems in their habitats that they can plug into. They’ve got an array of adaptations, whether it’s some of our vests that are still using and other bits and pieces. They’re quite a clever bunch of guys, and they’ll adapt things. Rick does that with his equipment too. They’ll adapt it and make it suit what they want, and they’re not afraid to change things.

Dressed for success!

I’m glad I asked you about that. Interesting. Just as an aside, I’ve been working with Harry [Dr. Richard Harris]. They are really pushing the limits of physiology on these dives and so we started looking at hydrogen—using hydrogen for the very deep portion of the dives. I organized a small hydrogen working group. Our focus has been to investigate how tech divers could use hydrogen breathing mixes to improve safety and performance. We focused on the Mule’s Pierce Resurgence dives as they were a great example. 

How far off do you think they are from bringing it in?

Good question! They’ve got a ways to go. Ha! The problem is testing. Do you just say, “Okay, it sounds good in principle though it’s never been done before, let’s give it a try for real.” Ha! I have a great video of Harry, Dr. Richard Harris, imitating Clint Eastwood’s Dirty Harry character, going, “Well punk, are you feeling lucky today?”

They are looking at hydrogen, which is, of course, half the molecular weight of helium, because at the depths they are diving (to 250 m/815 ft and beyond), the density of the breathing gas is around seven plus grams per liter (g/L)—quite a bit above Drs. Simon Mitchell and Gavin Anthony’s maximum, do-not-exceed limit of 6.2 g/L. Danger, danger! Any exertion at those pressures and gas density, and you’re liable to buy the farm!

I’ll never forget—I think it was at OZTek maybe ten years ago. They showed footage and were explaining about how heavy the gas was and how difficult it was to push around the loop. And everybody in that auditorium was breathing hard as Harry was talking.

Ha! It’s not a trivial problem to fix. They are actually considering ways to help move the gas around the loop, for example, like those used in Continuous Positive Airway pressure (CPAP) machines for sleep apnea, which pressurizes the gas—well in this case air—slightly above ambient. 

How would they decompress from hydrogen? Are there any tables?

Another good question! According to noted decompression physiologist, David Doolette, who was in our H2 group, that’s the least of their problems! There are a number of critical issues that the Mules are going to have to sort out to dive hydrogen. 

First, it’s explosive when mixed with more than 4% oxygen, hence only useful for deep depths. For example, a 4% oxygen mix at 250 m would yield a PO2 of 1.04—shallower than that and you’re not going to have efficient decompression. Also, H2 has five times the heat conductivity of helium, so they will likely have to heat the gas. Of course, heated breathing gas is standard for commercial and military SAT divers. It’s a crazy and yet intriguing idea.

It sounds like something that Elon Musk needs to get involved with!

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Right?! Instead of buying Twitter! Ha! They need a billionaire behind them for sure, if only to afford the testing that will be required. But it’s a real thing. I think at some point it will happen. The idea is to improve the safety and performance of conducting a 300, 310 meter dive, something like that—1000 feet over current methods. And of course, the word “safe” is really relative when you’re talking about doing surface-to-surface bounce dives to those depths. 

Did I ever tell you how we connected with the Mules?


It was through Rick Stanton. Harry mentioned it in an interview in “The Rescue.” He said something like, “This quiet unassuming English guy turned up who we had never met before, with a dry suit that looked like the best part of 20 years old.”

That dry suit was a 4mm neoprene that we used to make and the guy was Rick Stanton. That’s how O’Three came on the radar of the Wet Mules. That was about 15 years ago now. A couple of years into our relationship with those guys, I’m not sure whether it was Harry or Craig, but one of them told me that switching to neoprene (the Ri 2100) brought benefits that they were not aware of at the time; they just wanted reliable, dry, drysuits.

The benefits were the combination of streamlining and insulation that the neoprene suits gave them. The combination of those benefits reduced the effort, the exertion required to carry out those dives. They told me that the switch from trilam to neoprene was a game changer.

That makes sense. I remember Craig talking about the dangers of any exertion at those depths where just moving gas around the loop required an exertion because of the density of the gas. He said if you’re breathing is not calm and controlled, then you’ll soon be “behind the eight ball,” and things could go rapidly out of control. That’s what caused David Shaw’s death at Bushmansgat—respiratory insufficiency. Sadly, his video camera recorded his demise—respiratory insufficiency. 

Sorry to get us off track Sean. I just find this stuff fascinating. So looking into the future, what are your plans for O’Three going forward?

We’ve always been lucky from a staffing point of view. We have a few people that have been with us for a long time, but we have also got a great young team coming up. We’ve managed, not necessarily by judgment, but by luck, to reduce the [average] age of the team considerably over the last couple of years. And that’s a good thing for my partner Marcus and I going forward. We are hopeful that O’Three will continue. With the young team we have now, there’s no reason why the company couldn’t go on for another 25, 30 years. So, from a business point of view, we’re strong. 

I think, being really honest now, that some of our products have been designed to reflect how we think they should be built. But we need to look over our shoulder and realize that many of the new people coming into diving today want a slightly easier ride, if that’s good terminology. They want products that are easier to use. They might not perform as well, but then they are not doing the kind of diving that we expected them to do.

You’re speaking of recreational and or tourist divers.

That’s right. So we’re gearing up some products more suitable for the recreational diver because that is where the biggest part of the market is right now. We probably need to create a line that’s more user-friendly, shall we say, to get on and off. They might not perform as well, but these guys aren’t the Pierce Resurgence guys and they aren’t the Rick Stantons of the world. 

There are a couple of brands out there that have done well in that market, and we need to look at that going forward while not compromising what we do best, which is hopefully creating high quality products that will keep people dry and warm for many hours in temperate waters.

Thank you Sean. I wish you and your team the best of luck!

Michael Menduno/M2 is InDepth’s editor-in-chief and an award-winning journalist and technologist who has written about diving and diving technology for more than 30 years. He coined the term “technical diving.” His magazine “aquaCORPS: The Journal for Technical Diving” (1990-1996) helped usher tech diving into mainstream sports diving, and he produced the first tek.Conferences and Rebreather Forums 1.0 & 2.0. In addition to InDepth, Menduno serves as an editor/reporter for DAN Europe’s Alert Diver magazine, a contributing editor for X-Ray mag, and writes for He is on the board of the Historical Diving Society (USA), and a member of the Rebreather Training Council. 

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Configure Me This: The Annotated Sidemounter

We make a deep dive into the world of sidemount diving, and examine seven leading sidemount systems with guest editors Steve Davis and Stratis Kas.




This feature was created by Steve Davis, Stratis Kas and Michael Menduno. Introduction by Michael Menduno. Special thanks to Michael Thomas and brand representatives who helped us. Cover collage by SJ Alice Bennett with photos by Jason Brown of Bardo and Stratis Kas. Images by Stratis Kas unless noted.

🎶 Pre-dive Clicklist: Dave Brubeck – Take Five 🎶

At last, I am pleased to present InDEPTH’s long awaited sidemount edition, which has been in the works for over a year. The purpose of the issue is to celebrate the art and practice, as well as the equipment and culture of sidemount diving. Call it, “The Joys of Sidemount.” But whether you already follow the Bogarthian way, or simply regard it all as “widemount,” I promise you there is something for you in this issue.

The seed of an idea for a sidemount issue grew out of two things: First was the popularity and interest of our NOV 2021 feature that celebrated our innate gear headedness: “Annotated Tekkie,” which examined the question of what and how much kit is required to safely explore our underwater world. Diving is a technology-dependent activity to be sure.

Second, was, that we’ve been seeing tremendous growth and interest in sidemount diving we’ve been seeing. Like technical diving itself, what started in the cave community with small groups of experienced divers experimenting with DIY sidemount configs some three plus decades ago, has now blossomed into a mainstream, commercial tech diving activity in both cave and open water. Sidemount diving has now even spilled over into recreational diving—the configurational equivalent of recreational nitrox in the era of tech mixed gas diving.

One of the important inflection points was bringing sidemount diving out of the caves where the configuration was born, into open water. Sidemount pioneer Jeff Loflin was one of the individuals instrumental in bringing sidemount to recreational divers and the open water tech community. He explained it this way to me in our interview, “We were taking sidemount from the dark, and bringing it into the light.”

“We were taking sidemount from the dark, and bringing it into the light.”—Jeff Loflin

Interestingly, over the last decade, sidemount rebreathers, used as both a primary or a bailout, or both, have also gained significant traction driven by innovative vendors like KISS/XDEEP, SF2, Divesoft, and others. In fact, seven vendors are currently producing sidemount rebreathers. Note that we have also seen an increase in the number of chest-mounted units that can be integrated with sidemount systems. However, we decided to focus on open circuit sidemount for the purpose of this issue, andl address sidemount rebreathers at a later date.

Today, virtually all of the tech diving agencies offer open sidemount courses, with the possible exception of NAUITEC. For example, these range from “Intro to Tech” level sidemount courses, at RAID, which are aimed at getting divers into sidemount at the beginning of their tech journey. At the other end of the spectrum, Global Underwater Explorers (GUE) only offers a cave sidemount course to those who have completed GUE’s advanced cave training (Cave 2) and have at least 50 post-class cave dives.

Similarly, the majority of the major recreational agencies offer a recreational sidemount class for open water divers, including CMAS, NAUI, PADI, RAID, SDI, and SSI. Collectively, these agencies are issuing thousands of certifications a year.

So how big is sidemount diving? Good question, right?!?

How big is tech diving?!? We don’t really know. As an industry we suffer from a severe case of data insufficiency syndrome (DIS). [We can combat this—see our survey below!] However, in speaking with insiders involved in the sidemount business, some rough comparisons emerged.

Sidemount diving is likely bigger than rebreather diving, which according to estimates presented at Rebreather Forum 4 in April, likely represents about 15-20,000 divers globally. This seems like a plausible estimate given the significant cost difference, familiarity with the equipment, and perhaps greater accessibility to training and equipment with open circuit sidemount compared to rebreathers.

Sidemount rebreathers have gained significant traction. Here is Divesoft’s Joseph Bosquez diving a Liberty Sidemount in Ginnie Springs, Florida. Photo by Marissa Eckert.

Another comparison: sidemount diving is likely bigger than cave diving! “Sidemount is not just used for cave diving anymore, but I would say that at least 80% of cave divers have at least tried, or have sidemount in their tool kit. Fifty percent or more dive it exclusively,” Dive Rite general manager Jared Hires explained. Add in tech sidemount diving in open water and wrecks, and the growing number recreational sidemount divers, and we are likely to arrive at what sidemount instructor Steve Davis of Sidemount Pros estimates as “Cave divers plus some.” 

On the recreational side, a PADI exec told InDEPTH that PADI’s Sidemount Standard Specialty is now as popular as its Dry Suit Specialty, which is PADI’s third most popular Specialty Diver course, behind Enriched Air (Nitrox) Diver and Deep Diver, and ahead of Peak Performance Buoyancy. No drills on the knees, puhleez! I kid our friends at PADI.

Despite its growth and relative new-found prominence, sidemount still remains a kind of a best kept secret—the elephant in the restriction?—by which I mean many tekkies (including myself until recently) lack awareness and working knowledge of sidemount diving and may not have even tried it.

Not surprising divers being what they are, even among sidemount instructors and users, there’s a range of opinions on its use and application. On one hand, some view sidemount as a specific tool to be used exclusively for diminutive karst cave, on the other, many consider sidemount more of a platform choice. In fact, Davis, who you’ll hear more about in a minute, offered this question and assertion in our interview, Speaking Sidemount, and then went on and made his case:

 “Is backmount the best tool for cave diving? No, it’s not. Sidemount is far and away the best tool for cave diving!”—Steve Davis

Certainly, many including GUE, would challenge this assertion. But on the other hand, who died and left legacy twinsets in charge? Jacques Cousteau? Is backmount intrinsically safer? Does it offer better performance? If so, please share the data with everyone. There is room for respectful debate. Of course, every platform has its strengths and weaknesses, and environmental conditions, and individual physical and preference differences play an important role in choosing the appropriate platform. However, because of the lack of awareness, knowledge, and direct experience in the overall diving community, the limitations of sidemount get exaggerated, and its application, perhaps, under appreciated.

“There’s absolutely nothing I can’t do in sidemount that you can do in doubles, and there are a shit ton of things that I can do in sidemount, that you can’t do in doubles.”—Edd Sorenson

As instructor trainer and cave rescuer Edd Sorenson explains in his Who’s Who interview, “People used to tell me all the time all the things I couldn’t do in sidemount, and still do. ‘You can’t dive off a boat, you can’t do this, you can’t do that, you can’t scooter, you can’t double stage, you can’t quad.’ I would tell everybody the same thing. There’s absolutely nothing I can’t do in sidemount that you can do in doubles, and there are a shit ton of things that I can do in sidemount, that you can’t do in doubles.” Note in his interview Sorenson recounts taking GUE founder and president Jarrod Jablonski for his first sidemount dive. A trust me dive with Edd? Trust me, you don’t want to miss it.

Not surprising, it seems that many, or most of the dedicated sidemount divers we spoke to for this issue (See: The Who’s Who of Sidemount Diving) offered some version of the following, and or, would likely agree with this meme:

Once You Go Side, You’ll Always Dive Wide.

Ha! I kid our backmount sisters and brothers. None the less, it’s clear that sidemount is here to stay!

Now I’m not a sidemount diver, yet (it’s on my list), and only one member of InDEPTH’s team dives sidemount, in caves. So, to help us with the issue, we enlisted the help of two sidemount experts to serve as guest editors. We reached out to New Zealand-based sidemount instructor, ambassador, and host of the “Speaking Sidemount” podcast Steve Davis, principal of Sidemount Pros. We also enlisted the help of Greek photographer/filmmaker, author, long time InDEPTH contributor, and cave and sidemount instructor, the inimitable Mr. Stratis Kas. Both of them helped with the selection people and sidemount systems we planned to highlight, and authored content for the issue.

Beginning with this lead story, “Configure Me This,” we explore seven recognized and storied sidemount systems, all of them a little different. Who knew there were that many? In contrast, it’s fair to say, backmount configs have generally become fairly standardized in the global tech community. Please note, that the majority of models are shown wearing their personalized branded gear not necessarily stock products.

Next, we offer the perspectives and stories of 34 leaders in the field, in a piece titled, “The Who’s Who of Sidemount Diving.” We also dive into the philosophy, culture, and practice of sidemount diving in “Speaking Sidemount” and “The What, Which and Why of Sidemount Diving’‘ with our guest editors.

In addition, we offer A Brief History Sidemount Diving with Lamar Hires, Bill Renaker and Patrick Widmann, and specifically the evolution of cold water vs warm water sidemount titled, “The Evolution of Sidemount System Design: Two Distinct Paths Shaped by Florida and Mexico,” by sidemount instructor and author Andy Davis. Finally, the issue wouldn’t be complete with a bit of DIY sidemount heresy from long time scuba engineer and troublemaker, Dave Mclean, call it Sidemount Heresy! Trust me, you’ll be better for the exposure!

Here then is InDEPTH’s celebration of sidemount diving and culture. We want to thank our forward thinking sponsors: DAN EuropeDive Rite, DivesoftFourth ElementHalcyon, Shearwater and XDEEP for making this issue possible. We also want to thank Nicole Alarid, Orie Braun, Jared Hires, Nick Hollis, Michael Thomas, and Patrick Widmann, who helped us sort out sidemount configurations and Elena Vivaldo for researching recreational sidemount. And of course, we want to thank our models: Robert Thomas (CDG), Ricardo Castillo (Dive Rite), Emöke Wagner (Halcyon), Melodie Trevino (Hollis), Marcelin Nebenhaus (Razor), Mélissa Bezaz (Toddy) and Tamara Adame (XDEEP). Looking good divers! We do plan to create a free downloadable poster from this issue. Watch this space!

Please note, we realize this issue primarily represents the views of advocates who are making a case for sidemount. We haven’t focused on stories of divers who have had bad experiences with sidemount or spent much ink delving into its downsides, to the extent that these exist. Consequently, I invite readers who feel so moved to submit their views and or experience, call it, “The Trouble With Sidemount ” or “Never Do This is Sidemount..” . I’m joking about the titles but serious otherwise. We will happily run thoughtful stories. Let’s get a conversation going.

Finally, we would like to acknowledge that as human diving journalists and artists on deadline, we have likely made errors and omissions, and/or failed to identify important items that our geeky readers will no doubt discover. Our apologies in advance. If you do find any errors, omissions, or needed tweaks, please let us know, and we will endeavor make corrections. Thank you.—Michael Menduno/M2

Please take a minute and complete our new: Sidemount Diving Survey. We will report the results in a coming issue.

Use the following navigation links to dive into your favorite configurations 

Cave Diving Group

Dive Rite Nomad Ray

Halcyon ZERO GRAVITY™ Sidemount System

Hollis Katana 2


Toddy Style

XDEEP Stealth 2.0 Tec

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Cave Diving Group (CDG) Sidemount System 

The CDG sidemount system has evolved many times since the 1960s but it’s still a lightweight system for diving sump’s generally found after significant dry caving. The important thing to remember is that it is not just one system. Each diver will have a slightly differently made harness but basically doing the same thing. 

Photos courtesy of the CDG.
Weight System
  • Traditionally the weights go around the waist on a CDG harness, a more modern version of the CDG harness such as the RMTD harness (in the photo) weights can be fitted down the spine. 
  • The harness itself is a simple design with minimal adjustment but designed to walk or cave while wearing wetsuits and small cylinders. It can also be used with larger cylinders. Steel cylinders are the norm for uk cave diving. The harness has fixed D rings and no sliding D rings for use with Aluminium cylinders. 
  • Some CDG harnesses are adapted to use with vertical access equipment (SRT) so the caver/diver can descend the vertical dry cave then use the same harness to dive. 
  • The CDG harness has no wing, because generally buoyancy is not required when using wetsuits and small cylinders in sumps. It was common for divers in British Sumps when using drysuits to use the suit for buoyancy and use no wing. In more recent years a small wrap around wing such as the X deep classic or home made equivalent can be easily added if the diver is using bigger cylinders or carrying equipment through the sump to further dry cave exploration and requires buoyancy.

The CDG harness is designed to take weight loading on the divers’ shoulders and hips. Karabiners are generally used for attaching cylinders to the harness. A bolt snap is not a weight loading piece of equipment and should not be used to lower equipment down and then up vertical sections of dry cave, karabiners also work when covered in mud or grit! It’s not a harness that will get cylinders in that perfect internet trim but it is a harness designed to explore flooded cave sections found a long way underground. All modern harnesses took the sidemount system from the original Cave Diving Group harness design. 

Dive Rite Nomad Ray

The Nomad Ray is the latest sidemount system offering from Dive Rite. It includes a number of notable upgrades to the Nomad range and was designed to be easily adjustable, suitable for a range of body types and diving applications, including the use of both steel and aluminum cylinders.

Weight System
  • The Nomad Ray has three padded, internal pockets each of which can hold up to 5 lbs/2.3 kg of either hard or soft weight.
  • The weight pockets are located on the back of the wing and accessed via a zipper, making for easy weight adjustments while fitted.
Photos courtesy of Dive Rite.
  • The harness consists of independent shoulder, waist/hip, and crotch straps each of which are adjustable to fit the system to a variety of diver body types.
  • The harness incorporates custom hardware including two fixed angled D-rings on the shoulders, two fixed angled D-rings on the waist/hip strap plus, two sliding waist D-rings, two chest bungee-retainer slides, two rear drop D-rings for primary tank attachment, and one “dog-bone” crotch strap double D-ring for accessories, plus a DPV D-ring.
  • The harness is in Y configuration and attaches to the BCD/wing via woven D-rings at the top and through woven loops and screwed connection at the bottom.
  • For the fashion conscious, the wing comes in six colors.
  • The BCD wing is shaped to provide lift at the lower lumbar region. It comprises a Denier outer shell with an inner bladder and has 42 lbs/19 kg of lift.
  • The upper backside panel is abrasion-resistant for restrictions.
  • It incorporates a standard inflator that can be routed from the left (standard) or right side.
  • The BCD includes two pull dumps which are also OPVs. One is located at the inside top center of the wing with a left shoulder pull dump activated via a sheathed cord. The second is located at the bottom left of the wing. The locations of the dumps may require an alteration of diver position to dump all of the gas from the wing e.g. roll to the right to dump from the left side lower dump. Note this would also align with dumping gas from a drysuit. 
  • “Belly-band” bungees locate and wrap the outer wing extremities to the diver’s body. The bungee includes a bungee hook attachment and two wing grommets for easy and quick adjustments by simply moving an overhand knot on the bungee.

The Nomad Ray is a significant upgrade for Dive Rite and evolving to meet the needs of modern sidemount divers. In particular, the easy-access weight system, shoulder dump, easy-to-adjust “belly-bungee,” plus the method of attaching the harness and the independent crotch strap to the wing, are notable improvements.

Halcyon ZERO GRAVITY™ Sidemount System

Halcyon’s Zero Gravity sidemount system was a collaborative creation with our Mexico distributor, Zero Gravity. The Zero Gravity system puts the buoyancy over the hips and along the sides of the rib cage where buoyancy is desired. Extremely streamlined, the air chamber positioning gives it a flat profile on the back of the diver. The Zero Gravity is suited for double aluminum 80’s and a wetsuit or small steel cylinders used with dry suits and heavier undergarments. The Zero Gravity features an adjustable harness, and an optional weight pouch that will hold up to 15 lbs./6.8 kg, and optional inflator placements on the right or left side.

Weight System
  • The added weight attachment is designed and built to lay on the diver’s back in line with the spine. Like our traditional weight options, this allows the diver to keep perfect trim while adding weight. With the three-pocket design, you can add up to 5 lbs/2.3 kg in each pocket as needed and disperse them at different placements for that balanced distribution. The velcro additions allow for secure storage and keep even soft lead pouches from moving around while diving. 
Top left and right photo courtesy of Halcyon Dive Systmes.
  • A harness system with multiple point adjustment is styled after the standard backplate harness, with the lower portion of the strap going behind the diver, allowing for greater freedom of movement and comfort, especially for the women in the diving. This harness system is easily changeable when needed over time, allowing the diver to modify the colors of the webbing if desired for personal customization.
  • The newly redesigned door handles provide divers with several options when choosing the right cylinders and placement. With the added grommets, the diver can adjust the door handles into three different locations on the back, as is, higher, or in towards the diver’s back. This placement is essential when setting up the cylinders. The added feature of using curved door handles over traditional square door handles is that when the cylinders are clipped to the system, the bolt snaps do not snag or get hung up in a corner. This keeps the cylinders and the bolt snaps in a free space for easy reaching, clipping, and removing as needed throughout the dive. 
  • The adjustable bungees make it easy to use with different regulator configurations, whether the regulator is pointed up or down. The waist strap D-rings on the right and left hip allow for AL80’s to be clipped forward as they become buoyant. We achieve this with a non-fixed D-ring by adding an O-ring to the design. This allows the D-ring to be in an upright position for easy finding and clipping while at the same time allowing the D-ring to move freely if in a tight passage or corridor without becoming a snag point. 
  • The uniquely positioned cylinder bungee runs across the back of the system and diver giving you more stretch when wrapping your valves while keeping your cylinders high, tight, and secure. This placement of the bungee allows the diver to adjust the bungee length very easily, whether in training or for the more experienced sidemount divers. This bungee is very easy to change out by the user if they prefer a lighter or heavier bungee without compromising the design of the system.
  • The streamlined design with a unique U-shaped bladder provides an almost free and clean back that reduces your profile and drag. The U-shaped bladder allows stable, uniform lifting along each side of the diver where they need it and across the rear of the diver so they have adequate lifting potential without sacrificing profile and trim. This keeps the profile of the diver very low enabling them to access smaller passages without rubbing the bladder. Top to bottom while trim position does not change even as the bladder is fully inflated. This was a key component in the design for low-profile passages and doorways.

“As an avid sidemount diver and explorer in North Florida, I have used a variety of side mount systems on the market. It wasn’t until I dived the Zero Gravity system, that I was able to pass through several low passage tunnels without feeling the top of the system scraping along the way. The low profile of the system, even when fully inflated, allowed me as the diver, to keep a low profile in the cave system. This truly became a game changer when it came to exploring new tunnels.” Orie Braun, Halcyon Sales Manager

Hollis Katana 2

The Katana 2 is the latest sidemount offering from Hollis and brings them into line with the other top contenders in the sidemount space.

Designed with support from cave explorer Edd Sorenson, the Katana 2 incorporates a number of innovative features including a “Quick-Fit” system for easy adjustment, the ability to configure as a H or Y style harness, out of the box support for the KISS Sidewinder, and a BCD top dump valve with shoulder pull.

Photo courtesy of Melodie Trevino.
Photo courtesy of Hollis.
Weight System
  • The Katana 2 weight system features a drop-in Velcro pouch design with 4 x 5 lbs/2.3 kg pockets along the spine. The spine positioning of the weight system can assist with trim adjustment as required.
Photos courtesy of Hollis.
  • The Katana 2 sidemount harness features an innovative “QFS” Quick Fit System which allows users to easily tailor the one-size-fits-all harness to their specific size.
  • The design also allows for either an “H” or “Y” style harness configuration. H-style is most commonly used when donning the system in a drysuit and can be less restrictive, while the Y-style is most similar to a backplate configuration and provides a snug but comfortable fit when properly sized. Both are suitable for various types of diving and user preferences.
  • The Katana 2 is the first harness with attachment loops built-in to support the popular KISS Sidewinder CCR and similar units now in the marketplace.
  • The wing lift capacity is 40 lbs/18 kg and features a tapered design to keep the diver profile as low as possible, without the “turtle shell effect” which causes drag. 
  • The top of the wing is two- dimensional, versus the bottom which has a three-dimensional design for targeted lift placement to promote better horizontal trim. D-ring attachment points for accessories are placed on both sides of the wing, which are easier to reach than the traditional crotch strap attachment. The wing is also available in either a single or dual bladder option.The Katana 2 wing has a 1000D Nylon Cordura outer shell for abrasion and puncture resistance, and a 420D nylon inner bladder. The wing includes a top dump with shoulder pull that allows venting of gas while in trim.

“The coolest thing about the Katana 2 is the way it ships out of the box. You can customize it to your preference thanks to the innovative harness and adaptable wing design. Technical divers love to customize their gear … and they can make all of the adjustments themselves without permanent modifications on this rig.” Hollis Brand Manager, Nick Hollis


The Razor Harness embodies simplicity and elegance with just two continuous pieces of webbing and one closure point. Its design is minimalistic, yet strong, rugged, and reliable. The harness offers a comfortable and custom fit for divers of all sizes, thanks to its quick and easy setup and adjustable, standardized hardware.

Weight System
  • The Razor Harness allows precise placement of weights for optimizing trim. Additional weights can be easily added to the Razor Pocket Weight, the Waist Strap, or both if more than 13 lbs/6 kg are needed.
  • All attachment points, such as D Rings, on the Razor Harness can be swiftly and easily adjusted for personalized equipment placement. Each Shoulder Strap/Waist Strap can be adjusted at the Mini Back Plate.
  • The length of the Lumbar/Crotch Strap can be adjusted at the Delta Shoulder Plate. The height of the Waist/Hip strap can be adjusted at the Mini Back Plate. Extra attachment points can be added if necessary.
  • The BCD/wing is simple to use and attach or detach from the Razor Harness, secured by just two button head bolts. The mounting position can be easily adjusted to accommodate different-sized divers.
  • The wing is exceptionally durable, constructed with three layers: two outer layers of abrasion-resistant 1000 denier ballistic nylon with a layer of heavy gauge polyurethane in between. The wing is ultrasonically welded, and all edges are finished with edging tape. All attachment points feature reinforced grommets for added strength.
  • The primary wing provides 45 lbs/20 kg of lift and is equipped with a low-profile, heavy-duty manual dump/OPV valve from DSS, along with a standard power inflator. This allows inflation of the primary wing either using the power inflator or orally.
  • The fittings for the dump valve and corrugated hose/power inflator are interchangeable, enabling divers to use them on either the left or right side of the wing according to their preference.
  • The Redundant wing also provides 45 lbs/20 kg of lift and is fitted with a very low-profile “coin” dump/OPV valve and oral inflator.

The Razor Harness and BCD/Wing system offers divers a sleek and minimalist design without compromising on functionality or durability. Its simple yet robust construction provides a comfortable and secure fit for divers of all sizes. The weight system allows for precise weight distribution to optimize trim, while the adjustable attachment points offer personalized equipment placement. The BCD/wing is easy to attach and remove, and its rugged three-layer construction ensures long-lasting performance. With interchangeable fittings and low-profile valves, the system offers versatility and convenience. Overall, the Razor system combines simplicity, reliability, and versatility, making it an excellent choice for divers seeking a streamlined and efficient diving experience.

Toddy Style

The Toddy Style Sidemount System offers divers a unique and innovative approach to sidemount diving. Its “sandwich” style weight system, adjustable harness, and thoughtful design elements enhance comfort, balance, and ease of use. With the ability to customize weight distribution, easily adjust harness straps, and utilize specialized clips, this system provides divers with a streamlined and efficient sidemount experience. The Toddy Style Sidemount System is a reliable choice for divers seeking enhanced maneuverability and minimal drag during their underwater explorations.

Weight System
  • The “sandwich” style system consists of a thin backplate that holds the wing together while protecting it from accidental restriction impact. A backmount-style backplate finishes the sandwich-style system. These backplates also act as a weight system. If the user desires, additional backplates can be added, fitting perfectly on top of each other and distributing the weight evenly over the diver’s back, rather than concentrating it on the spine. This allows for better balance and reduces the “rotation” effect.
  • For divers who want to travel with the system, there is a more traditional sidemount weight system. It consists of a weight holder that can be added to the backplate, again placed away from the spine, to enhance balance and minimize the “rotation” effect.
  • Finally, there is a flexible butt extension with a special mount for precise addition of weight to achieve optimal trim.
  • The system’s shoulder straps are easily adjustable using a Velcro system that secures it in place with wide elastic wraps.
  • The shoulder straps are connected by a removable bungee that keeps them in place when divers turn on their side. It also acts as a temporary clipping place for items such as pigtail marker clips, lights, etc.
  • The inflator extends from behind, near the neck area, resembling the position in a backmount system. There is no valve, but instead, a direct, extremely durable, and resistant connector. This eliminates a fragile point present in all other systems.
  • The wing’s bladder is easily accessible and can be changed even in the field.
Regulator accessories
  • The system also utilizes custom-made clips for the regulator’s second stages. These clips allow divers to secure the regulators to their chest D-rings, resulting in a more streamlined profile and easy access in case of an emergency.

The Toddy Style Sidemount System stands out as a top choice among cold water backmount divers looking to transition smoothly to sidemount diving. It offers a convenient alternative because of its compatibility with both existing regulators and hose lengths, as well as not requiring dedicated cylinders. The presence of a backplate, reminiscent of traditional backmount setups, provides a sense of familiarity and ease of adaptation. Whether for cold water diving or any other diving environment, the Toddy Style Sidemount System offers divers a reliable and comfortable sidemount configuration to enhance their underwater experiences.


The STEALTH 2.0 TEC was designed for deep decompression diving and extended cave penetrations. It provides 42 kbs/19 kg of lift to support multiple cylinders required for advanced diving. It effectively manages gas movement and position to ensure stability, balance, and trim at any inflation level.

Photos courtesy of Mekan Photography.
Weight System
  • The Xdeep Stealth 2.0 features a customizable central weight system located on the spine. It can be adjusted to accommodate the maximum weight preferred by the diver.
  • Additionally, there are droppable weight pockets available in different sizes: S-size (2 x 4.4 lbs/2 kg), M-size (2 x 6.6lbs/3 kg), and L-size (2 x 13.2 lbs/6 kg).
  • For fine-tuning trim purposes, there are also trim pockets in M-size (2 x 4.4 lbs/2 kg) or L-size (2 x 6.6lbs/3 kg) that can be placed anywhere on the harness.
  • The harness is one universal size with a wide adjustment range. It consists of independent shoulder, waist/hip, and crotch straps, each made of different thicknesses and fully adjustable with tri-gliders to fit various diver body types.
  • The harness utilizes custom hardware, including two fixed large D-rings on the shoulders, two fixed D-rings on the waist/hip strap, and two rubber sliding waist D-rings (metal version available as an upgrade).
  • It also has two rear drop square attachments for primary tank attachment, a crotch strap D-ring for accessories below the dump valve, and a DPV D-ring.
  • The Y-configured harness attaches to the BCD/wing at the top.
  • The BCD wing is designed to provide lift at the lower lumbar region. It is constructed with a Cordura 1100 dTEX outer shell fabric and a Nylon 440 dTEX inner bladder with a 0.2 mm TPU coating. It offers 42 lbs/19 kg of lift.
  • The upper backside panel is abrasion-resistant for durability.
  • The BCD includes an inflator available in three sizes, with a standard length of 16″/41 cm (14″/36 cm and 19″/48 cm available upon request).The inflator can be routed from the left (standard) or right side.
  • One central low pull dump also functions as the system’s OPV.
  • Bungees keep the wing attached to the waist harness, ensuring a snug fit around the diver’s body.
  • The wing’s color combinations can be customized on Xdeep’s website:

The XDEEP Stealth 2.0 is a well-designed and versatile diving system that caters to the needs of deep decompression diving and extended cave penetrations. Its robust weight system, adjustable harness, and efficient gas management make it a reliable choice for advanced divers. The BCD/wing combination offers ample lift and durability, while the customizable options allow divers to personalize their gear. Note that the modular system can also be configured from recreational sidemount. Overall, the XDEEP Stealth 2.0 combines functionality, comfort, and performance, making it a strong contender for serious diving adventurers.

Please Take a Minute And Complete our New: Sidemount Diving Survey. We will report the results in a coming issue.

Steve Davis  is the producer and host of the acclaimed podcast, “Speaking Sidemount,” author of the books, “The Canterbury Wreck – A Diver’s Guide” and the eBook, “Sidemount Fundamentals.” He is a specialist sidemount diver/instructor, dives exclusively in sidemount, and is the principal instructor and founder of Sidemount Pros. Steve travels the world diving sidemount in caves, wrecks, and open water. Through Speaking Sidemount Steve’s mission is to share his passion for sidemount diving and provide a medium for the world’s top sidemount divers, instructors, and explorers to share their experiences and thoughts on sidemount diving.

Stratis Kas, a Greek-Italian professional diving instructor, photographer, film director, and author, has spent over a decade as an esteemed Advanced Cave instructor, leading expeditions to extreme locations worldwide. His impressive diving achievements have solidified his expertise in the field. In 2020, Kas published the influential book “Close Calls,” followed by his highly acclaimed second book, “CAVE DIVING: Everything You Always Wanted to Know,” released in 2023. Accessible on, this comprehensive guide has become a go-to resource for cave diving enthusiasts. Kas’s directorial ventures include the documentary “Amphitrite” (2017), shortlisted for the “Short to the Point” Film Festival, and “Infinite Liquid” (2019), which explores Greece’s uncharted cave diving destinations and was selected for presentation at Tekdive USA. Kas’s expertise has led to invitations as a speaker at prestigious conferences, including Eurotek UK, Tekdive Europe and USA, Tec Expo, and Euditek.  For more information about his work and publications, visit

Michael Menduno/M2 is InDepth’s editor-in-chief and an award-winning journalist and technologist who has written about diving and diving technology for more than 30 years. He coined the term “technical diving.” His magazine “aquaCORPS: The Journal for Technical Diving” (1990-1996) helped usher tech diving into mainstream sports diving, and he produced the first tek.Conferences and Rebreather Forums 1.0 & 2.0. In addition to InDepth, Menduno serves as an editor/reporter for DAN Europe’s Alert Diver magazine, a contributing editor for X-Ray mag, and writes for He is on the board of the Historical Diving Society (USA), and a member of the Rebreather Training Council. Menduno is the organizer of Rebreather Forum 4.

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