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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.

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!

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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Whole Lotta CHO2ptima Going On

Launched in early 2020, just as the pandemic was getting started, Dive Rite’s innovative chest-mounted O2Ptima, aka the CHO2ptima, is generating significant buzz among instructors and users as the hot new rebreather on the market. Accordingly, InDEPTH chief Michael Menduno sat down with general manager Jared Hires to explore Dive Rite’s latest purpose-built creation. Is there a CHO2ptima in your future (carry-on case)?




By Michael Menduno. Header image: Max Kuznetsov going through the Manhole at Ginnie Springs by Fan Ping. Other images courtesy of Dive Rite unless noted. Full disclosure: Dive Rite is a sponsor of InDEPTH.

🎶🎶 Pre-dive Clicklist: A Whole Lotta Shakin’ Going On by Jerry Lee Lewis

Various brands of mixed gas rebreathers have taken their turn in the spotlight over the years as a result of their functionality and innovation. In the early days of the 21st century, it was AP Diving’s pioneering rebreather, the Inspiration, followed by the KISS Classic, and shortly after, Inner Space Corp’s Megalodon that were grabbing all the attention. Later, the rEVO and Hollis PRISM came to prominence. The O2ptima drew attention. Poseidon had its day in the sun when Type R i.e., recreational rebreathers were a thing. Remember them? Of course, in recent years, the JJ-CCR, including GUE’s configuration, the Fathom, and Divesoft’s Liberty—both backmount and sidemount versions—have garnered significant community attention, and still do. 

However today, it is arguably Dive Rite’s unique and innovative rebreather, the O2ptima Chest Mount, aka “The CHO2ptima,” which was launched during the early days of the COVID-19 Pandemic, that is receiving considerable buzz in the market and garnering new instructors and users. Ironically, while the community collectively moved to back-mounted counter lungs (CL) to free up chest space, Dive Rite has taken a different approach altogether, and moved its rebreather to the front of the diver, reminiscent of combat divers units (offering optimal CL placement when in trim), and that’s only part of its novelty. 

Weighing in at 7.7kg /17 lbs and able to fit in a small carry-on roller case, its compact size along with its ability to interface with practically any open circuit configuration—from Rec to Tec—to drive it, makes CHO2ptima a serious choice in travel rebreathers. As the tagline says, “Dive Rite—Equipment for Serious Divers.” Interestingly, many divers, including some GUE members, are considering the CHO2ptima as their next rebreather.

Accordingly, we reached out to Dive Rite’s 31-year-old General Manager Jared Hires, who has been diving rebreathers since he was 15, to take us for a deep dive into their newest rebreather. Hires, who is an active, advanced Technical Diving International (TDI) tech and CCR instructor, and an apprentice cave instructor with the National Speleological Society-Cave Diving Section (NSS-CDS), explains the philosophy behind the CHO2ptima and its development, discusses its use and applications, and talks about the possibility of getting the unit CE-tested, so it can be sold in Europe. 

I conducted the interview with Jared while he was in between duties managing the nearly 40-year old family business, and teaching a CHO2ptima class. Here is what the man had to say.

InDEPTH: Dive Rite launched its O2ptima backmount rebreather in 2006. Then, in March 2020, you launched the O2ptima CM, aka “The CHO2ptima”—a modified O2ptima with chest-mounted counterlungs. I get the distinct impression that the CHO2ptima has surpassed its predecessor’s sales by quite a bit, and there’s considerable buzz around the unit. Is that an accurate characterization?

Jared Hires: The CHO2ptima has gained a lot of attention since its release, and sales have surpassed the backmount version. I think this can be attributed to several different factors. Since the unit is integrated into a diver’s primary gear configuration, they are less apprehensive in making the jump to a CCR. There is less of a learning curve since everything is not new.

Another contributing factor is cost. The CHO2ptima is extremely affordable (by rebreather standards), which is making it more attainable for divers. I would like to think that we have grown the rebreather market, not that we have just taken a larger portion of the pie.

Jared Hires sporting his CHO2ptima

What’s the retail price?

$6,900 with a Shearwater Petrel 3 controller or $7,200 with a NERD 2 Controller.

Wow. That is very affordable. Lamar [Hires] told me that CHO2ptima sales really made a difference during the pandemic!

Releasing a new rebreather at the start of a pandemic was hard. It was difficult to get it out there for people to see and to get instructors up to speed. Somehow, we were able to do it. It was a welcomed addition to our line and helped the business continue to grow through the pandemic. We have been extremely busy.

So, how did the CHO2ptima come about? What was the motivation?

It was a long project—something that we were working on for at least three to four years. During that process, we tried out many different concepts and renditions. It all really stemmed from the fact that sidemount rebreathers had started to become popular, and we had people asking for them. People were wondering if we were going to offer one since we had already made a name for ourselves in sidemount. We were the first to offer a commercially-available sidemount rig and one of the pioneers in sidemount diving. It seemed natural that we also have a spot in the sidemount rebreather market.

I remember some of Lamar’s early sidemount units that he developed with Woody Jasper and Wes Skiles back in the day.

That’s right. Of course, we also had a very strong background in rebreathers working on producing the O2ptima since the mid-2000s and having lots of units on the market. So we started working on a concept. 

One of the things that held us back from sidemount rebreathers, especially early on, was the fact that all of the units at the time, like the SF2 or the KISS Sidekick, featured a single sidemount rebreather attached on one side, and most divers, particularly around here, wore a single bailout bottle attached on the other side. And a lot of people still do that. We didn’t really like that idea. 

We are cave divers, so it’s all about redundancy. You won’t see many of us going into a cave with only one bailout bottle. Some people in Florida were using a bailout bottle with an H-valve, so they at least had two regulators. That was a little bit better, but there were still quite a few people not carrying what we thought was adequate bailout. So that kind of turned us off on the idea of doing just a straight sidemount unit. 

Other integrated sidemount units, like the KISS Sidewinder, which has been really popular, alleviated the issue of bailout because the diver carried a bailout bottle on each side, which provided adequate bailout gas. The drawback was that it had to be completely integrated into your sidemount system. So, it wasn’t something that you could take off mid-dive if you were exploring and had to pass through a tight restriction. You essentially had to dedicate a complete sidemount rig to nothing but that. And we just didn’t like the concept of that either.

The idea was to modify Dive Rite’s O2ptima rebreather, right? 

That’s right. We wanted to keep as much of the O2ptima intact as possible—especially the scrubber design—we really liked the Micropore scrubber. It’s always easy to pack consistently. There’s no user interface when it comes to having to pack a scrubber. We also wanted to keep the electronics—we wanted a fully electronically controlled rebreather and not a manual rebreather. We didn’t want to have to sacrifice any of the features that we had come to enjoy on a traditional back-mounted O2ptima. So that’s why we started looking at the chestmount as an option rather than sidemount.

The chestmount would actually allow you to add it to any type of diving system. You could add it to any sidemount harness, you didn’t have to make modifications to an existing sidemount harness,and you didn’t have to worry about integrating it in and dedicating a rig to nothing but that. But it would also work with other configurations like back-mounted doubles or even a single tank.

Diver with backmount doubles and the ChO2ptima

So, the CHO2ptima started out as an exploration tool for sidemount—a sidemount rebreather concept, but it has now evolved to become a travel rebreather, basically, or an add-on rebreather to any open circuit configuration. People are diving them with a single tank, doubles, and sidemount.

I don’t know if all our readers know this, but a chest-mounted counterlung is optimal from a work of breathing perspective, assuming that you’re in trim. That’s why combat divers, who kick long distances, wear chest-mounted oxygen rebreathers.

That’s right. One of our design philosophies with the CHO2ptima, and actually the O2ptima as well, has been to keep the breathing loop as short as possible. Even on the backmount unit, the scrubber is right behind the diver’s head. As a result, our hoses and the counterlungs can be smaller since it’s got a shorter breathing loop. 

As you said, the lungs are right below your lungs, so also it’s not just the fact that the work of breathing is better, but even your change in buoyancy from breathing. That was one of the issues with sidemount rebreathers, the ones that go completely on your side. Every time you breathe, there is a slight shift in buoyancy and you will tilt to the side. Everyone will tell you that you just have to get used to it. But you can eliminate that by putting the lungs in the same exact position as your lungs as we did with the chestmount.

I know I felt relief went I went from over-the-shoulder counter lungs to back mounted counter lungs. How do your users feel about having the counter lungs over their chest? Does it feel cluttered or difficult to manuver?

I felt the same relief moving to backmounted lungs from the over the shoulder lungs on the O2ptima, and had some apprehension about the chest mounted ChO2ptima. The main relief felt with backmounted lungs is the ease of carrying bailout. You get the same relief with the chest mounted unit, especially if you’re using it with a backmount open circuit configuration. I can carry a lot more bailout comfortably with the ChO2ptima than I can with a BM unit. 

With the way the counter lung bag is shaped, most of the bulkier parts are lower down, so you really have the free use of your hands, and the chestmount does not get in the way on working dives. Even when diving in sidemount, I have easy access to my drysuit inflation and power inflator.

The rebreather is attached to the diver’s existing open circuit rig and is set up so that the diver can actually remove it during the dive; for example, in order to go through a restriction. That’s totally unique in itself.

For sure! That was one of the features and purposes that we envisioned for the unit. Generally, when we design equipment, we have a purpose for it. We don’t just set out to say, “Hey, we want to make a new gadget.” I like to think that sets our equipment apart from other dive gear manufacturers. We don’t just come up with a new color for something and release it as a new product. 

The CHO2ptima can be donned, removed and reddened underwater, and thus staged.

When we come up with something new, it has a purpose, whether it’s to make it easier to do a certain dive or alleviate a problem that divers have. 

Lamar definitely had in mind the ability to remove the unit underwater when we were designing the CHO2ptima. There are a couple of exploration dives that he had left off and wanted to go back to.

Yes, in the interview we did a few years ago, I remember Lamar talking about going back to Cow Springs. 

Yeah, his thought was, I want to be able to dive my rebreather all the way up to this tight restriction and basically remove and leave it, go through the restriction, do some exploration on open circuit going through these tight restrictions, come back out, grab my rebreather, and exit the cave. So, to do that, we wanted something that was completely independent. 

We also thought about travel. If divers are traveling and/or diving with friends, maybe they don’t want to dedicate a whole dive trip to a rebreather or dedicate all their dives to a longer dive or a bigger dive. We do this all the time when we go down to the Keys, for example. So, maybe in the morning we’re going to do a deep wreck dive with some decompression. I can carry a single 95 on my back with my CHO2ptima on the front, and stage a deco bottle. But then, in the afternoon, maybe I’m with my wife or with friends that are just diving a single tank dive on Molasses Reef, and I don’t want to have the complexity of a rebreather added into that dive. So, I just leave the rebreather on the boat and still have my same full configuration. We do that quite often.

So, it gives the diver maximum flexibility. That makes sense. I was at Bonaire Tek last Fall, and friends showed up with their CHO2ptima in a little roll-away travel case. It was impressive.

That’s right, when I travel, the whole rebreather, plus extras, fits in a carry-on Pelican case. And it was not just the rebreather. I had lights and all kinds of extra stuff in the carry-on case and the rest of my dive gear can go into its normal suitcase. That’s it. The unit itself only weighs 7.7kg /17 lbs.

When I travel with my backmount unit, it takes a large suitcase for the rebreather and another one for my camera and the rest of my dive gear. I barely have room for two swimsuits.


What I find most intriguing and unique is that the CHO2ptima can basically be worn with any sort of open circuit gear. 

Yeah, to add the CHO2ptima to any harness, to any configuration, all it takes is two attachment points on your shoulders and two attachment points on your waist. Some people are able to use the D-rings that they already have on their harness. However, I usually add an additional set that I dedicate just to the unit because I like the top attachment points to be up closer to my clavicle. And then I just add an extra set of D rings to my bottom. Two clips on your shoulder straps and two clips on your waist strap is all you need to add the unit. Then there’s a single low pressure inflator hose or whip to plug the unit into your back gas or to your side mount tanks or whatever. The only thing extra on your kit is a single additional inflator hose. 

The unit itself contains the scrubber, head, and oxygen cylinder.

That’s right. However, some people mount the O2 offboard, which you can do. You can carry your O2 as a stage cylinder, especially if you’re carrying a deco stage anyway, and you weren’t planning to drop it like some of the ocean guys do. So basically, everything else is selfcontained except for a diluent feed hose.

What were some of the challenges in packing all that functionality into a very small space?

It was a bit like trying to pack 10 pounds of shit in a 5 pound bag. That was definitely a challenge, but we were not willing to sacrifice any features.

The scrubber is in the middle, and then you have the head on one side, and the cap on the other side is basically a water trap—it’s the same exact module that we use on the back-mounted O2ptima. So that was the easy part. One of the biggest challenges was designing the outer bag, so it would accommodate most divers. Something that would fit a really tall guy wouldn’t fit someone who was petite. So we had to do some work on that. The counterlung design was also a big challenge. We went through multiple iterations trying to find just the right size that would provide good work of breathing but not add too much to the size of the unit.

The lungs are inside the unit?

Yes, the whole bag assembly contains your inhale and exhalation counter lungs in the bag. We had to do a lot of work on the designs of those counter lungs to make it all work. And there were little things along the way. We worked through several renditions of water trap designs, and we went through several Diver Surface Valve (DSV) designs and changed up some of the fittings to make them work just right. We looked at using an actual sidemount type DSV where the fittings came off of the DSV and went down. We ended up putting the elbows on the actual bag instead of putting them on the DSV to give it more of a natural feel. We also changed bag materials and added a pocket for accessories. 

What about for women divers? Do their breasts get in the way?

Luckily, wetsuits and drysuits take care of most of that for us. They actually act like a corset. So that hasn’t really been too much of an issue. The only people that maybe struggle are the guys with the big beer belly. We have a few of those in the community, but even for those guys, the CHO2ptima works pretty well. Big guys, like myself, don’t have a problem. However, the one group that has problems with a stock unit without making modifications are super short people. Because of the actual length of the unit, they may have issues. But that’s just with the standard mounting hardware. Many of these people can make a few adjustments to a stock CHO2ptima and have zero issues.

I see that you are also continuing with the Micropore scrubber cartridges, which are basically pre-packed scrubber cartridges that eliminate the need to hand pack the scrubber with sorb. I know that the military loves them. Are there other civilian rebreathers that use them?

I think we are currently the only vendor that is actively promoting the use of cartridges with their unit. When we first started using the Micropore cartridge in the early 2000s, there were some other ones. Most notably KISS had started using the cartridge—they actually made some units that were only able to work with the cartridge. Another was the Titan rebreather.

The French chest-mounted rebreather?

No, not the Triton but the Titan—the original one that was basically a backpack. It used Micropore cartridges. And we built the original O2ptima with the idea of using cartridges. At that time, 2003, 2004, the idea of cartridges was starting to pick up steam. So, there were a few units that used them, and divers were also making adapters for the AP Diving’s Inspiration, which was one of the first commercially available mixed-gas units on the market, as well as a few other rebreathers, so that they could use the Micropore cartridge. 

We bought into the concept, and still do—we think it’s the right way to do it. You remove the potential for user error in filling the scrubber, and it’s consistent and solid. That’s what’s written on the packaging, “A Solid Choice,” because you don’t have granules to deal with. Everything is exactly the same. People were using the extender cartridges because of the benefits. A lot of O2ptima users tell us that the cartridges are one of the reasons they like the unit. Of course, both the O2ptima and CHO2ptima unit can use granular sorb as well, so you are not locked into the Micropore cartridge.

You can do either one?

Exactly. Our scrubber was actually designed in collaboration with Micropore to give our unit the best work of breathing, the best duration and the best efficiency with the cartridge. So that was the main goal.

At the time, the mid-2000s, there was a big after market for conversions. A lot of divers were upgrading their units with Hammerhead Electronics, which was the gold standard of the day, and many were also having us add Dive Rite harnesses and buoyancy devices to their units, and as I mentioned, many were adding adapters to be able to use cartridges. 

Let me ask you about electronics. I know that you started with Hammerhead electronics on the O2ptima, but then eventually migrated to Shearwater electronics, which of course has become the de-facto standard in the tech market.

Yes, Hammerhead was a collaborator of ours. Our original units had Hammerhead electronics. We used them all the way up until about 2013. I believe it was the very beginning of 2013 when we made the switch to Shearwater. So, we had a long relationship with Hammerhead, and a great relationship with founder Kevin Jurgensen. He remains one of the pioneers in the rebreather world, and he’s a great guy. Unfortunately, there were others that came to market, and they were not able to keep up.

Shearwater was able to bring new technology to the market, both with their computers and rebreather controllers. They created a lot of buzz when they released the Predator in 2009 and they continue to do so.

I think JJ-CCR was the first rebreather manufacturer to go with Shearwater.

Yes, I believe JJ was first. Then others such as rEvo and Hollis started integrating them as well. After the Predator was released, we had many divers asking us to integrate them into the O2ptima. Some sent us in Fisher connectors to attach to their rebreathers so they could run a secondary Shearwater computer. A lot of our instructors and distributors were big Shearwater fans.

We finally met with Shearwater at the DEMA tradeshow in 2012. Later that year we got our first set of electronics, added them to the O2ptima and started doing test dives through the early part of 2013. I think we actually released the new unit at Beneath The Sea (BTS) 2013 using DiveCan and the Petrel controller.

I have a few more questions about electronics. Solid-state oxygen sensors? Is that something you are looking at, thinking about?

If they ever become readily available, yeah, we would look at them. And if Shearwater bought into the concept and integrated them into their technology, then we would, of course, look at it. We take the lead from them when it comes to sensor technology. Solid state sounds cool in theory. The thing is, you always have to have redundancy, so you’d need two of them at least. For sure, it would be awesome if you didn’t have to change out your sensors every 12 months.

How about scrubber thermal sticks and gaseous CO2 sensors. 

The sticks are not really CO2 sensors, but they do measure scrubber duration.

Right. They’re distinct from gaseous sensors. Only a few vendors are using either of these.

Thermal sticks are being used by a couple of manufacturers, most notably AP and rEVO. They track scrubber usage by looking at the temperature fluctuations caused by the chemical reaction of the scrubber. Thermal sticks tend to be an add on upgrade and not standard.

Some companies are also starting to use CO2 sensors as well, though they have not been widely adopted yet. The issue that we have seen with CO2 sensors is that they’re large. So, integrating one into a small package rebreather is hard. Another issue is that they don’t like moisture, and a rebreather is inherently a moist environment. The byproduct of the reaction in the scrubber is moisture— water and heat. They require extra precautions and consumables like desiccant packs to absorb the moisture. If those precautions are not strictly followed the sensors can produce false alarms. Eventually, if a diver gets too many false alarms, they become complacent and ignore the alarms altogether.


I know of many instructors who tell their students not to buy the CO2 sensor upgrades due to their finicky nature. Especially if diving in high humidity environments like the Caribbean.

But, when someone comes out with a sensor that is smaller and more reliable i.e., more humidity tolerant, then I think it would make a good additional alert. Remember that scrubber breakthrough is not completely linear. Breakthrough is exponential at the end of the scrubber life. When it breaks through, it’s an, “Oh Shit Moment,” and you need to bail out right away. 

Lamar Hires discussing the CHO2ptima
Assembling CHO2ptimas at Dive Rite in Lake City, FL. Photos by Fan Ping.

Let’s talk about building the unit. You build the CHO2ptima in the US right?

The ChO2ptima is assembled right here at our headquarters in Lake City, FL. We partner with other small companies here in the US for our machined parts and sewn pieces. But everything is brought into our factory in pieces to be assembled from scratch and to go through the rigorous final quality control check. 

The most tedious part is integrating the raw electronics that do come from Shearwater in Canada. From start to finish, a single rebreather head takes a minimum of 3 days to go through the different steps. This includes multiple components that are potted and over 300 solder points.

Made in America! That will no doubt appeal to some users. Talk to me about who is actually using the CHO2ptima.

The ChO2ptima is worldwide with divers across North America, South America, Asia, and Australia. This is one of the areas the pandemic hurt us with the launch, because instructors were not able to travel as easily to get up to speed on the new unit. That’s why we have started with a better stronghold here in the US because we could reach those instructors easily.

We are starting to get some interest in Europe and have a few divers using the unit there, but it’s limited because the unit is not currently CE approved. This may be something we pursue in the future for a bigger expansion.

I’ve heard that the cost of CE testing is somewhere between US$50,000-US$100,000.

We have gone through CE testing for many of our products over the years and based on those experiences, the figure is more on the high end of your range. It is a lot harder and more expensive for non-European companies to do as well. The issue is that you have to pay for the testing to be done at a European facility most of the time and then do all the paperwork and the documentation to their liking. A lot goes into it besides what the test house does, which adds even more to the cost

We do know that Rebreathers require proper testing before divers can trust them with their lives. We’ve done all the main CE tests through a third-party testing facility here in the US called Dive Lab. We have a blog on our website that has all the results from that and some pictures of it going through testing if you want to take a look at that. That would be in addition to the hundreds of actual dive hours on the unit by our in-house test divers, myself included.

Another neat aspect about our relationship with Micropore, is they actually have an American National Standards Institute (ANTSI) testing machine on site. We do a lot of testing there. Every time they do a production run of scrubber material, they do a quality control check of the scrubber material in a Dive Rite rebreather, whether it’s the back-mounted O2ptima or the CHO2ptima, in the ANTSI testing machine. I don’t think many other sorb companies are testing their product in an actual rebreather for quality control after a production run, which is kind of cool.

It is! What agencies support CHO2ptima training?

A number of them, though I would say that TDI and IANTD are the main ones. Most of the instructors have a TDI or IANTD qualification, and some have additional ones on top of that. I know that we have a couple of PSAI instructors and a few PADI instructors that can teach Tec 40 and up on the unit. Global Underwater Explorers (GUE), of course, only teaches its specially configured JJ-CCR and the RB-80.

Interestingly, the CHO2ptima is actually broadly compatible with GUE’s CCR configuration i.e., two diluent cylinders in doubles configuration with a long hose and secondary in addition to the loop, when worn with doubles. (See “The Thought Process Behind GUE’s CCR Configuration”)

I dive a DIR configuration on my doubles kit. You’re looking at a card-carrying Fundamentals diver, though I haven’t done anything past that, but I dive a DIR setup for sure. With the CHO2ptima you can easily dive it in a DIR configuration. And probably a little bit easier than you can even with JJ-CCR. It’s a lot easier to deploy a long hose—you don’t actually have to bail out to deploy it with the CHO2ptima, which we’ve already known has caused issues. There have been people that have flooded units in the process of trying to donate gas.

Jared Hires diving the CHO2ptima with back mount doubles

Practice, practice, practice, right?!? We covered the development and working of the CHO2ptima. Talk to me about some of the exploration that’s being done. I know that people like Steve Lambert are doing some incredible new stuff at Peacock Springs. [See: The Taming of the Slough: P3 Edition]. Talk to me about some of the projects people are using these for.

We’re lucky. People like Steve are doing some really cool stuff with the unit. He’s was one of the catalysts that helped push the ChO2ptima over the finish line when he came to work for us. He was excited about using the CHO2ptima just like Dad and a couple of the other guys were. He volunteered to be one of the test divers and immediately started doing big dives with it. 

He’s been doing some great exploration and has gotten a couple of his buddies from Karst Underwater Research (KUR) and “Beyond the Sump” into CHO2ptimas. They just came back from that expedition in Huautla (See: Sump Potion No. 9). They had two divers on CHO2ptimas, one on a KISS sidewinder, one on a JJ-CCR and two of them on Fathom units. So the CHO2ptima was well represented down there and they were doing some awesome dives with that. 

They’ve been working hard in Peacock and exploring in Peacock 3 down deep in Henley’s Castle. They also did some really deep exploration at Chaplain in early 2021, which is another deep spring up here and I was lucky enough to do one dive with those guys. It’s 55 m/180 ft deep for most of it—a deep river cave. We also have people who are doing deep ocean dives with them. Ben Lair, one of our CHO2ptima instructors based in Arizona, has done a number of deep wrecks in the 92 m/300 ft plus with the unit. So, there definitely are people that are doing some cool stuff with it. It’s not just doing tourist dives, that’s for sure.

Diving the CHO2ptima with a sidemount configuration. Photo courtesy of Fan Ping.

And how about Lamar? Wasn’t he planning to use one at Cow Springs?

Yeah, Cow was one of the big ones that he wanted to do. And he’s gone back and has definitely checked out those leads that the CHO2ptima was designed for. Unfortunately, I guess he let the cat out of the bag to a couple of his friends that also went and checked out the leads before he could.

Ha! I guess you have to keep your mouth shut in cave country! Thanks for taking us through the unit, Jared. Wishing you continued success with your rebreathers.

See our companion story, Taming the Slough: P3 Edition by Steve Lambert

Additional Resources


CHO2ptima Reviews:

PodDiver Radio: Optima CM: Chest-mounted CCR Review

Dive Addiction: ChOptima ECCR Review (Dive Rite Optima CM)

The Dive Locker: Chest-mounted Rebreather Dive! Choptima (O2ptima CM) Action!

For more information on scrubber cartridges: Micropore

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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