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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.

  • Buddy Dive Bonaire

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!

  • Buddy Dive Bonaire

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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InDepth’s Holiday Rebreather Guide: 2022 Update

Making a list. Checking it twice. Gonna find out which breathers are naughty or nice. That’s right! It’s time again for InDEPTH’s Holiday Rebreather Guide.
This year, the Guide features 28 models of back, chest, and side-mounted rebreathers, including two new entries, for your shopping operation. So, get out your pre-buy checklist, and that gift certificate and start ogling your loop of your fancy. Ho ho ho!




InDepth’s Holiday Rebreather Guide: 2022 Update

by Michael Menduno, Amanda White and Kenzie Potter

Holiday images by Jason Brown, BARDO CREATIVE

A Guide to Backmount, Sidemount and Frontmount Rebreathers

1DEC 2022—Ho ho ho! Once again, we have updated InDEPTH’s Holiday Rebreather Guide adding two new rebreathers; the new Gemini sidemount, needle valve mCCR from Fathom Systems, and the Generic Breathing Machine (GBM) front mounted, needle valve mCCR, with a dive computer-compatible, solid state oxygen sensor from Scubatron. We also updated the features on the Divesoft Liberty sidemount, and the JJ-CCR. This year, Vobster Marine Systems was acquired by UK-based NAMMU Tech, which plans to rename and re-issue a version of the VMS Redbare. See link below.

Finally, Innerspace Systems’ founder Leon Scamahorn agreed to work on getting us the needed information to add the storied Megalodon to the Guide. Scratch last year’s coal, Xmas cookies for you Mr. Scamahorn! Happy holidays shoppers, here is our updated rebreather guide! Mind those PO2s!

17DEC2021: Ho Ho Ho! We have updated our Holiday Rebreather Guide with new rebreathers and updated features. Despite repeated requests, the only major closed circuit rebreather we are missing is Innerspace Systems’ Megalodon and its siblings. Tsk, tsk Leon Scamahorn, you’ve been a naughty boy! Behold, here is our updated guide. Mind those PO2s!

Sport diving rebreathers have come a long way since storied explorer Bill Stone trialed his 80 kg/176lb fully-redundant “Failsafe Rebreather For Exploration Diving” (F.R.E.D.), and spent a cool 24-hours underwater as part of his paradigm-shifting 1987 Wakulla Springs Project. In retrospect, looking back over the last 30-some years, the “Technical Diving Revolution,” which emerged in the late 1980s to late 1990s, was ultimately about the development and adoption of rebreather technology. 

Dr. Bill Stone’s manned trial of F.R.E.D. at Wakulla Springs (1987). Photo courtesy of the US Deep Caving Team

However, it took the fledgling tech community at least a decade to adapt mixed gas technology for open circuit scuba, including establishing the necessary supporting infrastructure, which was the first and necessary step in the move to rebreathers. A little more than a decade after Stone showcased FRED, British diving entrepreneur Martin Parker, managing director of then AP Valves, launched the “Buddy Inspiration,” the first production closed circuit rebreather designed specifically for sport divers, earning him the moniker, the “Henry Ford of Rebreathers.” [The brand name later became AP Diving] KISS Rebreathers followed a little more than a year later with its mechanical, closed circuit unit, now dubbed the KISS Classic. The rest as they say, is history, our history. 

Buddy Inspiration advertisement from 1998. Courtesy of AP Diving.

Today, though open-circuit mixed gas diving is still an important platform, rebreathers have become the tool of choice for deep, and long exploration dives. For good reason, with a greatly extended gas supply, near optimal decompression, thermal and weight advantages, bubble-free silence, and let’s not forget the cool factor, rebreathers enable tech divers to greatly extend their underwater envelope beyond the reach of open circuit technology. 

As a result, divers now have an abundance of rebreather brands to choose from. Accordingly, we thought it fitting this holiday season to offer up this geeky guide for rebreather shoppers. Want to find out whose breathers are naughty or nice? Here is your chance.

Your Geeky Holiday Guide

The idea for this holiday guide was originally proposed to us by Divesoft’s U.S. General Manager Matěj Fischer. Thank you Matěj! Interestingly, it doesn’t appear to have been done before. Our goal was to include all major brands of closed circuit rebreathers in back mount and sidemount configuration in order to enable shoppers to make a detailed comparison. In that we have largely succeeded. We  also included Halcyon Dive Systems’ semi-closed RB80 and more recent RBK sidemount unit, which are both being used successfully as exploration tools. 

Absent are US-based Innerspace Systems, which makes the Megalodon and other models, as well as Submatix, based in Germany, which manufactures the Quantum and sidemount SMS 200, neither of which returned our communications. M3S, which makes the Titan, declined our invitation to participate, as they recently discontinued their TITAN CCR—they will be coming out with a replacement unit, the TITAN Phoenix CCR in the near future. We did not include the MARES Horizon, a semi-closed circuit rebreather that is aimed at recreational divers. No doubt, there may be brands we inadvertently missed. Our apologies. Contact us. We can update.

Update (22JUL2021): French rebreather manufacturer M3S contacted us and sent us the specs for their updated chest-mounted Triton CCR, which are now included in the guide.

Update (9DEC2020): Submatix contacted us and the Guide now contains their Quantum (back mount) and SMS 200 (sidemount) rebreathers. We were also contacted by Open Safety Equipment Ltd. and have added their Apocalypse back mounted mechanical closed circuit rebreather.  We will add other units as they are presented to us by the vendors. 

It’s The Concept, Stupid

The plan was to focus on the feature sets of the various rebreathers to provide an objective means to compare various units. But features by themselves do not a rebreather make. As Pieter Decoene, Operations Manager at rEvo Rebreathers, pointed out to me early on, every rebreather is based on “a concept,” that is more than just the sum of its features. That is to say that the inventors focused on specific problems or issues they deemed important in their designs; think rEvo’s dual scrubbers, Divesoft’s redundant electronics, or integration of open and closed circuit in the case of Dive Rite’s recently launched O2ptima Chest Mount. Shoppers, please consider that as you peruse the various offerings. My thanks to Pieter, who helped us identify and define key features and metrics that should be considered.

Though not every unit on the market has been third-party tested according to Conformitè Europëenne (CE) used for goods sold in the European Union, we decided to use CE test results for some of the common feature benchmarks such as the Work of Breathing (WOB), and scrubber duration. For vendors that do not have CE testing, we suggested that they use the figures that they publicize in their marketing materials and asked that they specify the source of the data if possible. As such, the guide serves as an imperfect comparison, but a comparison nonetheless.

Santa’s Little Helper: Meet Rufus, BARDO’s Chief Muse Officer (CMO)

Also, don’t be misled by single figures, like work of breathing or scrubber duration as they serve only as a kind of benchmark—there is typically a lot more behind them. For example, whether a rebreather is easy to breathe or not is a function of elastance, work of breathing (WOB) and hydrostatic imbalance. In order to pass CE, the unit must meet CE test requirements for all three issues in all positions from head down, to horizontal trim, to being in vertical position (Watch that trim!), to lying on your back looking upwards. It’s more difficult to pass the tests in some positions versus others, and some units do better in some positions than others. 

The result is that some of the feature data, like WOB, is more nuanced than it appears at first glance. “The problem you have is people take one value (work of breathing for instance) and then buy the product based on that, but it just isn’t that simple an issue,” Martin Parker explained to me.  “It’s like people buying a BCD based on the buoyancy; bigger is better, right? Wrong! It’s the ability of the BCD to hold air near your centre of gravity determines how the BC performs. With rebreathers you can have good work of breathing on a breathing machine only to find it completely ruined by it’s hydrostatic imbalance or elastance.”

Due to their design, sidemount rebreathers are generally not able to pass CE requirements in all positions. Consequently, almost all currently do not have CE certification; the T-Reb has a CE certification with exceptions. However, that does not necessarily mean that the units haven’t been third-party tested. 

Note that the guide, which is organized alphabetically by manufacturer, contains the deets for each of their featured models. In addition, there are two master downloadable spreadsheets, one for back mounted units and one for sidemount. Lastly, I’d also like to give a shout out to British photog phenom Jason Brown and the BARDOCreative Team (Thank you Georgina!), for helping us inject a bit of the Xmas cheer into this geeky tech tome [For insiders: this was Rufus and Rey’s modeling debut!]. Ho, ho, hose!

With this background and requisite caveats, we are pleased to offer you our Rebreather Holiday Shoppers’ Guide. Happy Holidays!!

Ed. note: Most prices shown below were specified by manufacturer before tax.

Backmount Rebreathers

* In 2005, AP Diving launched its Vision electronics with In-Plane Switching (IPS) which enhances colour and visibility
**Typical scrubber duration using AP Tempstik increases practical duration to more than double CE test rate figures – as the AP Tempstik shows scrubber life based on actual work rate, water temperature and depth.
*** The work of breathing is the effort required to push gas around the breathing circuit BUT that figure alone is meaningless without knowing two other parameters: Hydrostatic load and elastance. Note that AP Diving rebreathers meet the CE requirements in all diver attitudes for both Hydrostatic Imbalance 0 degrees (horizontal, face down) and Hydrostatic Imbalance +90 degrees (vertical, head up.)
**** APD’s handset offers a “dual display” feature showing data from both controllers on the same handset. The user can also see the gradient factors chosen and the mVolt outputs of the cells by holding a button down.
* Divesoft will offer an upgrade for existing Liberty users

* Note that we plan to re-release our “Intervention CCR” (iCCR) in 2021. The unit was withheld due risk of loop being force dived when unsafe (pending re-release 2021).This enables the diver the option to manually trigger bailout to a known safe OC gas at any time with one finger and/or auto-bailout the diver if loop gas being breathed reaches unsafe level. Either Hi/Lo PPO2 or high End-Tidal CO2.
**For CE certification the recommended Apocalypse Type IV CCR scrubber duration is 2hr 45min to a maximum dive profile surface to surface of 100m in 4’C water to 2.0% SEV (20mb) at the mouth.
***iCCR (2009) 3x digital galvanic coax, iCCR (2021) x2 galvanic 1x solid state
****All performance data near near identical to single scrubber option other than increased scrubber duration of up to 5 hrs to 100 m profile in 4’C water)
Published Testing: .pdf
* CisLunar series, MKVI 2009, SE7EN 2013, SE7EN+ 2019
** 40 m coldwater EN14143
*** Backmounted Trimix 10/70, 40M test: Backmounted Air
**** SE7EN+ Sport EU incl (harness, wing, computer, cylinders and sensors)

NOTE: Vobster Marine Systems were acquired by UK-based NAMMU Tech, which plans to rename and re-issue a version of the VMS Redbare (formerly the Sentinel) at some point in the future. See: Atlas CCR


Rey says he’s sticking to open circuit. What’s a Santa to do?

Sidemount Rebreathers

*Pre 2021 units are upgradebale
* For a tour of KISS rebreathers see:

Frontmount Rebreathers

*Tested with standard DSV, 6l OTS counterlungs, Upright/face forward, 40 m depth, 40.0 lpm RMV, Air diluent
**Tested with standard DSV, 45° head up/feet down orientation, 40 m depth, 40.0 lpm RMV, Air diluent
*** Micropore ExtendAir Cartridge:
180 liters of CO2 @ < 50 deg F [<10 C] (130 minutes @1.35lpm CO2)
240 liters of CO2 @ 50-70 deg F [10-20C] (180 minutes @ 1.35lpm CO2)
300 liters of CO2 @ >70 deg F [>20C] (220 minutes @ 1.35lpm CO2)
Test Parameters: 40 lpm RMV 1.35 lpm CO2130 fsw (40 m) depth Granular duration may be similar, but can vary greatly depending upon the type of granular and packing technique

 Download our two master spreadsheets, one for back mounted units and one for sidemount to compare rebreathers.

Special thanks to Amy LaSalle at GUE HQ for her help assembling the feature spreadsheets.

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Michael Menduno is InDepth’s editor-in-chief and an award-winning reporter and technologist who has written about diving and diving technology for 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. He also produced the first Tek, EUROTek, and ASIATek conferences, and organized Rebreather Forums 1.0 and 2.0. Michael received the OZTEKMedia Excellence Award in 2011, the EUROTek Lifetime Achievement Award in 2012, and the TEKDive USA Media Award in 2018. In addition to his responsibilities at InDepth, Menduno is a contributing editor for DAN Europe’s Alert Diver magazine and X-Ray Magazine, a staff writer for, and is on the board of the Historical Diving Society (USA)

Amanda White is the managing editor for InDepth. Her main passion in life is protecting the environment. Whether that means working to minimize her own footprint or working on a broader scale to protect wildlife, the oceans, and other bodies of water. She received her GUE Recreational Level 1 certificate in November 2016 and is ecstatic to begin her scuba diving journey. Amanda was a volunteer for Project Baseline for over a year as the communications lead during Baseline Explorer missions. Now she manages communication between Project Baseline and the public and works as the content and marketing manager for GUE. Amanda holds a Bachelor’s degree in Journalism, with an emphasis in Strategic Communications from the University of Nevada, Reno.

Kenzie Potter Stephens is a production artist for InDepth as well as part of the GUE marketing team. She earned her BS degree in Industrial Engineering and Marketing at the Karlsruhe Institute of Technology (KIT) in Germany, which assists her in using her multicultural upbringing to foster international growth within the community. In addition to her activities as a yoga teacher and an underwater rugby trainer, she has completed her GUE Tech 1 and Cave 1 training and is on her way to becoming a GUE instructor. Not letting any grass grow under her feet, she has also taken on a second major in biochemistry in order to create a deeper understanding of our planet’s unique ecosystems as well as the effect of diving on human physiology.

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