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My Journey Into Sidemount Rebreathers

With a growing number of users making the transition, sidemount rebreathers are the “New New Thing” in diving technology, especially in cave country. Here, award-winning underwater cameraman/photographer Becky Schott, who is also a rebreather and tech diving instructor, explains her motivation and experience finding the right tool for the right job!

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By Becky Kagan Schott

When I began diving twenty-five years ago I heard the phrase, “A good diver is always learning,” and in many ways I’ve lived by that motto throughout my entire diving career. I’ve been humbled underwater, and I’ve had days when all of my training and years of experience have come together, allowing me to create inspiring imagery with my camera. I wouldn’t be able to do that without experience and the thirst for knowledge. Leave your ego out of it. I mean, we all have one, but the environment doesn’t care if we are male, female, black, white, young, or old, so your ego won’t help you much, but being humble will. I practice skills frequently. I teach others to stay sharp and pass along my knowledge and most of all, even as an accomplished tech instructor, I am always finding new techniques and trying new things. I still take classes and seek mentorship from more experienced divers. I am always learning.

A few years ago while shooting a cave exploration documentary in the Abaco Islands in the Bahamas with Brian Kakuk and Brett Hemphill, I found myself back on open-circuit sidemount, although I prefer to be on closed-circuit rebreather (CCR). We had several stages, and I pushed a large Red Epic Camera along with me. I find open-circuit sidemount to be the most difficult configuration for me to film in. Constantly checking gauges, changing regulators, and moving tanks around, while trying to keep the camera steady and focus on the environment around me, as well as simultaneously directing a team of divers, is challenging. I’ve always enjoyed diving sidemount, and after that shoot I had a handful of other projects that required yet more sidemount diving.

I’ve always felt there is no reason to move on until you have a need to, and after twelve years on backmount CCR, I finally found I needed another tool, a sidemount rebreather. I began a yearlong process of looking at different units, demo’ing some, and talking to explorers and people way more experienced than I in sidemount CCR. For over a decade, one of my best dive buddies, Evan Kovacs, dived a Prism Topaz sidemount unit, and several other dive buddies use them, so I wasn’t that unfamiliar with them. I had a list of options that were important to me, and I began to talk to manufacturers and to watch as more divers started making the transition.  

Becky outside of Ginnie Springs. Photo courtesy of David Schott.

In the end, I chose the Divesoft Liberty sidemount unit because I liked that it is neutrally buoyant and can be clipped off, just like a traditional sidemount bottle with no fuss. It has both onboard diluent and oxygen (O2)  cylinders, a water trap in the counterlung that sits up high against your chest, a 5.5 lb radial scrubber (short), and its clean design with the Manual Addition Valves (MAV) running up the loop to the Diver Supply Value (DSV) (i.e., mouthpiece), which makes adding diluent or O2 manually very easy. This is a clean design, and while I’m shooting I’m not fumbling around looking for any MAVs. There is also an Auto Diluent Valve (ADV) that can be activated by just breathing, if you’re in a head-down position or if you need more loop volume. I found that to be really nice for descents. The unit has sophisticated electronics that some divers may like or dislike.

I thought it might be overwhelming, but a lot of thought has gone into everything on this rebreather. I like the built-in checklist and the ability to make a lot of personal adjustments in the menu system. The calibration is easy, and the unit walks you through predive checks, including positive and negative checks, even showing millibars of pressure. I also like that it’s sold ready to dive with little tinkering. Travel is important to me, and the unit is just 50 lbs/23 kg in a pelican case (minus tanks). Lastly, it has several modes that include CCR, manual CCR (mCCR), and a bailout rebreather mode that I may use down the road.

Putting It to the Test

I was nervous about how I’d feel on a sidemount rebreather after years of diving various backmount units. I put the DSV in my mouth and opened it up—at first a little awkward because I was standing on the steps at Ginnie Springs. I went horizontal in the water and descended into the basin. I immediately felt comfortable and made a few small adjustments, like moving the unit to a D-ring further back and adjusting the loop hoses into a more comfortable place under my arm. I couldn’t believe how well it breathed and the ease of activating the ADV or manually adding gas using the MAVs.


Giant Cave is possibly the largest sea cave on the planet! It’s located just off a dock in Caye Caulker Belize. The cave can spring and siphon and little is known about timing it. This was my 3rd trip to the cave and the first two times it was springing slightly and this trip it was siphoning enough to suck you in. The video is shot with a Paralenz dive camera of Becky Schott entering the fissure crack and first chamber on a Liberty Sidemount rebreather, then buddy Anthony Tedeschi going through the 100ft of restriction on his KISS Sidekick.

After becoming certified on it, I spent another 15 hours practicing skills in open water and then another 20 hours in the first 500 ft/152 m of Devil’s Cave system, just practicing and getting used to the idiosyncrasies of the unit and pulling random drills on myself. Changing set points is easy; I like the vibrating to give you alerts, and the Heads Up Display (HUD) and buddy light are easily seen. I took a camera, and it felt really natural to me. I had fun learning this new tool and gliding through the cave, and it felt really streamlined and clean. It was actually the most comfortable I’ve ever felt in sidemount. I used it with my Hollis Katana harness, and everything trimmed out nicely and felt comfortable in the water.  

In my opinion, a sidemount rebreather is an incredible tool, but it doesn’t replace a backmount unit. It’s a tool for a specific environment or purpose. Like any rebreather, it’s important to put the time on it and practice your skills to become proficient.

I spent more time with it back home in Dutch Springs. That was fun, considering it was March and the water temperatures were a balmy 37 degrees Fahrenheit or 3 degrees Celsius. I had no issues with dry gloves, but everything did take me a little longer to get together in colder water, wearing thicker undergarments. I had added Shearwater transmitters and an offboard gas addition supply, since it didn’t come with any. That’s important to me, and I easily added one to the unit. I added the transmitters to clean it up because I found it difficult to read the gauges or button gauges under my arm.

A Belize cave project suddenly came up at the end of March. This is exactly the reason I wanted a sidemount rebreather and a perfect project with friends. I’d been to Giant Cave and Winter Wonderland on several past trips, so I was also somewhat familiar with the systems. I decided I wouldn’t change my configuration too much and continued to dive drysuit, but instead of a steel tank, I went with an AL 80 in the warm water since the unit is neutral.


Schott liberty giant cave. Photo by Anthony Tedeschi.

Giant Cave is an advanced cave system that’s located off the island of Caye Caulker in Belize, and the entry is in the ocean just off a dock. It’s fascinating in many ways, but one thing that can’t be timed is when it’s siphoning or springing. It siphoned every time I entered the cave that week, making visibility less than 2 ft/0.6 m. It’s a challenge because you drop down a hole that narrows into a small fissure crack that you have to go through head down about 40 ft/12m into another open chamber before squeezing through about 100 ft/30 m of restriction that goes up and down sandhills and twists and turns.

There are also other considerations when diving a sidemount CCR, such as water traps; flooding; work of breathing; positioning; bailout planning; and how many cylinders to take and types (H valve or multiple tanks). There is a lot to consider and, as always, more to learn.

Luckily the jellyfish weren’t there this time so they weren’t siphoned in with us! I’ve done this entry almost a dozen times in the past but never in a siphon when I couldn’t see, and never on the sidemount rebreather. I knew the head-down position was going to be tough, and breathing might be hard during that time. I went for it and before getting to the bottom, in no visibility, I got tangled in the line. Inverted and unable to breathe, I signaled to my dive buddy and safety diver Anthony Tedeschi for some assistance. He was on a KISS Sidekick but he’s been diving it for over four years. He helped me out, and I caught my breath as I descended less than gracefully into the open chamber below. I caught my breath easily since the ADV activated, and I manually added diluent to get a proper loop volume. At this point, a lot of sediment was getting sucked into the cave, but we could see the line, and we slowly followed it in, passing crabs, sponges, and little coral pieces. Once through the restriction, the cave opened up into a huge room, and the visibility was clear. We had a good dive and shot some great video that day.

Exiting the cave was a similarly uncomfortable experience, as now I had to go vertical again, but in a head-up position where all the gas wanted to push its way out of my mouth. It’s a different feeling, trying to hold it in and only let out little bits. If you let out too much, you’ll drain the counterlung. The head-up and head-down positions are the biggest things to get used to. Going slightly head up or down is no problem, but being vertical is more challenging.  

Each day the entry and exit became easier as I committed to the entry and just went without hesitating. Once inside the huge, clear cave system, I could easily stay in horizontal trim, which is where the sidemount rebreather performs best.

Final Thoughts

I’m so happy I took the Liberty with me to Belize for this project. It’s probably the most challenging cave I’ll ever take it to, and it was a great tool for this particular shoot. We dived for a few hours each day, and I’d usually have only a few tablespoons of water in the counterlung and nothing in the canister. After a week in two different sea caves, both sidemount entrances, I was very happy to have gained experience that was totally different than my dives in the Florida caves on the unit. My plan is to continue to gain hours on it, in all types of environments, so that when opportunities arise, I’m ready and more confident. It’s important to me to have the tools that can help me do my job as an underwater image maker and be safe while doing it. I’m looking forward to putting more time on the sidemount CCR and taking it to some awesome locations this year. So far it’s been a fun new journey practicing, and enjoying silent sidemounting.


Becky is a five-time Emmy award-winning underwater cameraman and photographer whose work appears on major networks including National Geographic, Discovery Channel and Red Bull. She specializes in capturing images in extreme underwater environments including caves, under ice, and deep shipwrecks. Her projects have taken her all over the world from the Arctic to the Antarctic and many exciting locations in between, filming new wreck discoveries to cave exploration and even diving cage-less with great white sharks. Her biggest passion is shooting haunting images of deep shipwrecks in the Great Lakes. Becky is a frequent contributor to numerous dive magazines, both US-based and international, and her photography has been used in books, museums, and advertising. She is also a technical diving instructor and leads expeditions all over the planet. www.LiquidProductions.com    www.MegDiver.com

Cave

They Discovered an 11,000-year-old Submerged Ochre Mine

The exploration crew at CINDAQ, headquartered at Zero Gravity Dive Center in Puerto Aventuras made international news this year with their discovery of an ancient submerged ochre mine. Fortunately, they were happy to share the secrets of its discovery and how they documented their find with British cave and 3D photogrammetry instructor John Kendall. Oculus Rifts anyone?

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By John Kendall
Header image courtesy of
CINDAQ

In 2017, underwater cave explorers Fred Devos, Christophe Le Maillot, and Sam Meacham found evidence of ancient mining activity while exploring and mapping new tunnels of an underwater cave near Akumal, Quintana Roo, Mexico.​ Historians know that ancient residents actively mined pigment and other minerals from the caves of the Yucatan Peninsula, but the ancient mines the CINDAQ team discovered are now submerged, indicating that such mineral exploitation occurred thousands of years ago. 

At the end of the last Ice Age, intrepid miners ventured deep into these tunnels with torches in hand. The navigational markers, mining debris, fire pits, and excavation pits they left behind are now entirely underwater. Over the last three years, the three explorers (along with others) have been surveying the site and making 3D photogrammetric models of the mine workings. As the mine has been submerged for around 8,000 years, it’s been untouched since then, and it’s an amazing time capsule. The project recently hit the international news when the first results were published. I was pleased to be able to chat with Chris, Fred, and Sam to find out a bit more about the project, and the challenges faced with archaeological work in a cave environment.

The InDepth Word Cloud: A map of the frequency of words spoken in this interview.

John Kendall: How did you happen to find the mine?

Fred Devos prepping for a dive.

Chris Le Maillot: As always, there was a little bit of chance involved with it. The cave—Sagitario, which is a beautiful cave behind Minotauro—was initially explored by a few local cave divers. They established an upstream and part of a downstream, dropping down in the upstream to around 22 m/72 ft, and there’s the halocline sitting at that depth. It’s not always the case, but they didn’t take any survey, absolutely nothing. So I don’t think the information was there for them to continue on with the exploration. As you know, once you have that data in and have a good concept of what the cave is doing and where it’s going, it’s easier for you to poke around and find potential continuations of the cave passages. 

Chris Le Maillot.

So one of the divers asked Fred [Devos] to get involved to create a survey. That comes from the fact that Fred previously had done some mapping for these guys. Fred had a cave survey class coming up, so he took the class there, and spent the week with the survey class mapping the downstream part. Obviously, when they got to the end of the line, Fred could see that there was potential for further exploration. But you can’t really go off exploring during a class, so he went back with Sam [Meacham].

Sam Meacham before a dive with the team in La Mina.

So then you went back and explored?

Fred Devos: Exploring caves is what we’ve been doing for more than 20 years, and so it’s a regular event during the mapping of a cave to find more cave to explore. You know, when mapping, we have to swim off to measure the side walls, sometimes there isn’t a wall, and then end up exploring that passage. I was in the process of making a detailed map of this cave, and found this passage, so I went back with Sam, and we immediately realized something was unusual. Things were out of place, we started seeing rocks piled on top of each other, speleothems in places they shouldn’t have been, and the further we went the more of this we saw. 

“Exploring caves is what we’ve been doing for more than 20 years, and so it’s a regular event during the mapping of a cave to find more cave to explore.”

We started picking up a little bit of flow, which is always a good thing in exploration, and that led us to this restriction, where all the water was going through, and I don’t think we’d have made it through if the restriction hadn’t been manipulated before we got there. So, you know, speleothems were smashed out, and it really looked like 100 divers had gone through there before us, which really piqued our curiosity as we knew no one had been there before us. We happened to be in back mount during this dive and I managed to squeeze through there and called Sam through, and that was when we first saw irrefutable evidence of what humans had been doing in this cave—you know, pre-8,000 years ago. 

“It was pretty clear to anyone what we were seeing, that people had been digging in here, smashing open the floor and pulling out huge amounts of sediment and piling stuff out of the way. It was super exciting.”

An ochre extraction pit found by divers from Centro Investigador del Sistema Acuífero de Q Roo (CINDAQ A.C.) in the oldest ochre mine ever found in the Americas, dating back 10,000-12,000 years. Photo courtesy of CINDAQ.

We didn’t have to wait for lab results to come back or ask an archaeologist about it. It was pretty clear to anyone what we were seeing, that people had been digging in here, smashing open the floor and pulling out huge amounts of sediment and piling stuff out of the way. It was super exciting, as it was something we’d suspected for quite a while but had never really determined for sure that was what we were seeing. But this time it was obvious, and there was no question about it. 

So, how large an area does the mine occupy?

Sam Meacham: It’s about 250 m/817 ft of cave passageways that are exemplary of the mining activity, and everything we’re seeing there shows the things that people were doing in the mine. 

Devos: And we haven’t finished exploring yet. There are hectares of mining area, so it’s not just one hole that’s been dug out. It’s entire passages and we’re talking about hundreds, maybe thousands of tons of material, and remember we have dates spanning maybe a 2,000-year period.

What makes La Mina so significant from a scientific point of view?

Devos: The amount of workings means that this was a massive undertaking. Not just the mining itself, but it’s clear it wasn’t just a one-person adventure. It must have been multi-generational, but beyond that it speaks very much about the organization of the people of that time. So as you can imagine, they were in a dark cave and needed fire for light. So they needed people to bring in the firewood, and others to cart out the material, and there were probably explorers at the time. You know, people that ventured further into the caves away from the exit into the smaller passages…to find this very valuable resource. And I imagine they were the ones that were being punished somehow because the risk involved was probably much greater. So, you know, if they didn’t do their work well in the mine, they probably got sent to explore.

A diver making notes as he examines an ochre extraction pit . Photo courtesy of CINDAQ

So are there any archaeological signs on the surface around the mine?

Devos: Well there probably are, there’s certainly Maya era archaeology, and in almost every cave we see evidence of that, but we’re talking about 5,000 years ago. The mine was even further back, so anything that was once there won’t be anymore, and the only place we are likely to find anything is in the caves.

Let’s chat about the photogrammetry side. More and more people are hearing about photogrammetry, but I think the readers will be interested to hear a bit more about the challenges that you faced doing photogrammetry in a cave environment, where everything around you is archaeological.

Meacham: I think that can get us started on an interesting concept. In 2010, Chris, Fred, and I, Beto Nava, as well and Franco Attolini and Danny Riordan and Roberto Chavez, all did our underwater archeology course here in Mexico with the Nautical Archeology Society that was supported by the National Institute of Anthropology and History (INAH). It empowered us. 

And by having that NAS certification, it kind of helped check a box for the Institute. And, you know, they could say if anybody questioned our abilities, well, we’ve got the certification. 

I’d say the genesis of this for all of us here was the Hoyo Negro project, and with the exploration followed by the high grade survey, and then the photogrammetry, which is another whole level in itself. The major problem in Negro is the pit itself—it’s just immense—and how do you document something like that? So we worked with Beto and the team who came up with a grid system at 34 m/110 ft depth, and then it’s every 0.8 m/2.5 ft with a cookie on the line, and so it’s a systematic grid. The difficulty there is that it’s not just a nice flat bottom, it goes from 40 m/130 ft to about 55 m/179 ft, and it just becomes really complex. 

But basically what I’ve been doing there is assisting with the lighting or helping Beto. So when we jump forward to doing the mine, it’s a completely different environment. There’s no pit—it’s a continuous cave—so there was no way we could put in a grid, and I’ve never really done photogrammetry before. I had observed it being done, but I was starting from scratch in terms of my own experience. So it was a challenge, but I had plenty of people to go to as resources, and who could check out what I’d done and help make it better. And what’s interesting about the big model is that you can see my progression as we go around, and now of course I want to go back and do it all over again.  

So in terms of the challenges, I bought a Sony A7S camera and a Nauticam housing for it, and we just went in and started taking a bunch of photographs, came back, and put it into Agisoft. I have to say my expectations were low, but we were all pleasantly surprised when the model came back. This is like, “Wow that’s what we’re actually seeing there,” and it’s so cool. So that gave me the confidence to say, “I think I can do this,” and we basically picked about 250 m/817 ft of cave passage, which is a great example of the mining activity and of seeing what people were doing there. 

That sounds like quite a learning curve, and a big challenge. 

Meacham: Yes, we just started going in and piece by piece doing sections of the cave. I can’t remember how long in total we were down there. I’m sure it’s written down somewhere, but we took something around 18,000 photos. And as you know, taking the photos is probably the easiest part. Having the computing power and post-processing of the images is the key. A lot of people treat Agisoft as a bit of a black box, but you know it’s garbage in, garbage out. So in terms of the environment, we’re talking about a ceiling height that’s minimal, and while you can fit through OK, you want to be as high as possible for the photogrammetry in order to cover more area. 

“I’m sure it’s written down somewhere, but we took something around 18,000 photos. And as you know, taking the photos is probably the easiest part. Having the computing power and post-processing of the images is the key.”

So, we just worked section by section, using the line as a reference. I was going down the line and started by making sure that I got any markers on it, and then going back and forth to get all the photos. The person that suffered the most was whoever was assigned to dive with me, as they just had to sit there and watch me go back and forth while taking the photos.

18,000 images! That’s a whole lot of processing.

Sam Meacham: Yes, we’re lucky to have the guys at University of California at San Diego (UCSD) helping us with the processing. I probably started off taking too many photos, but the computer guys complimented us on the photos and the overlap and coverage. 

A landmark of piled stone and broken speleothems left 10,000-12,000 years ago by the earliest inhabitants of the Western hemisphere to find their way in and out of the mine. Photo courtesy of CINDAQ.

So what about other survey techniques, was there anything special about mapping this site?

Devos: We surveyed the first part of the cave, and that was pretty normal, but once we found the mine, then suddenly we had a need for all these new types of symbols that didn’t exist before for cave survey. I tried to think about what would be interesting to make notes of, but I didn’t want to speculate as to whether something was a natural pit or whether it was digging. 

The mine holds some of the best-preserved evidence of the earliest inhabitants of the hemisphere. Photo courtesy of CINDAQ

So we came up with three new symbols. There was already a symbol for a pit, but we added a jagged line on the pit to show that there was a broken edge, so it was smashed. Then we came up with a symbol for a displaced object, so if you see some stalactites and there was no way it came from the ceiling above, then that’s a displaced object. And then if you have stacked objects, so objects placed on top of each other, we had a symbol for that. We then made all of these colored red. I chose red because of the extracted material, the ochre. Also, when you look at the map, and you see all that red, it really shows the extent of the manipulation of the cave. It really brings it out, and I think that’s the most important thing about this cave. Sidewall information is nice, but this is very much an archaeological site.

So what’s next with the site? Any further diving plans?

Devos: We have some plans in place. The map that we’ve made, the photogrammetry, and the video documentation, even the exploration are not finished. So we actually concentrated on one area and tried to get that in the bag, you know, and focus our studies and our samples in that area, without stretching too far, but there’s still a huge portion to go. The technology really helps here, because you can bring that information out for the scientists and others to see. And then there’s much less need for others to go back there. 

And this is really the part where we don’t know what’s going to happen. Are divers one day going to be able to go there to tour this site? Luckily, I’m not the one who will be making that decision; there is an archaeological department in Mexico who set the rules. But these conversations are starting, and we’re not really sure where they will lead. But for now we are doing what we can to secure the documentation of the site and working closely with the archaeologists and the landowner. 

A CINDAQ diver noting details of the mine. Photo courtesy of CINDAQ.

So a last question: What would your advice be to a diver who is just starting out on their GUE journey, and who hears about this and other projects, and wants to one day join?

Devos: We have been running all kinds of projects down here for years: exploration, science, surveys. Come and get involved, and help out. Good basic training helps open up the door. 

Meacham: Once you’ve trained and gained enough experience to become confident in whatever environment you’re interested in, then come and get involved. There’s great training with the GUE Documentation Diver program, Science Diver, Photogrammetry Diver, and Cave Survey where you can actually put these skills to the test. Everyone on a project is an important part of making it work. Obviously it becomes tricky when archaeology is involved, as there can be federal laws and regulations that restrict access, and so we can’t always put just anyone onto a site, but there are all sorts of projects within GUE to help develop those skills and get known by project leaders.

Le Maillot: Of course, project diving is what GUE has been known for since the very beginning. So I think making that initial step to take training with GUE is an important one in the right direction. That’s the starting point of understanding how we are organized, the procedures that we use, [and] the team aspects of all our diving. And then it’s about thinking about what you want to do. 

“Of course, project diving is what GUE has been known for since the very beginning. So I think making that initial step to take training with GUE is an important one in the right direction.”

If you’re interested in wrecks, you have Mario Arena in Sicily or Richard Lundgren with the Mars project, and you’re naturally going to be headed down the Tech 1/CCR route. If it’s the stuff in Florida, or Bosnia, or here in Mexico, and the cave thing really rocks your boat, then that’s where the GUE cave training comes in. Then, as you progress with your tech or cave training, you will get to know divers who are involved in projects, and that could be your instructor. You know, if you come here to do some cave diving in Mexico, then Fred is going to mention a few things about survey and cave projects in Mexico and around the world. So that will start opening up a different perspective for you. 

Additional Resources:

InDepth: Data for Divers: Mexican Explorers Go Digital to Chart Riviera Maya

Watch a Video of the Mine on GUE.tv. (Requires a GUE.tv membership or signing up for a free trial)

For more information about the La Mina project, you can visit the CINDAQ website

Check out the CINDAQ YouTube channel


John Kendall is a GUE technical, cave, and CCR instructor living in the UK. Since he was a small child, John has been fascinated by the underwater environment and the possibilities of adventure, and he is grateful to GUE for helping him to turn those childhood dreams into reality. As an instructor, John regularly travels around the world teaching GUE classes and helping to build local GUE communities. For the last 5 years, John has been working with underwater 3D Photogrammetry as a technique for nautical archaeology. This cutting edge technique allows for digital 3D models to be created of shipwrecks and caves, and allows researchers and scientists unparalleled abilities to manipulate and navigate the sites from the comfort of their own computers. John was the primary author of the GUE Photogrammetry class. He is also a member of the GUE Training Council and a Fellow of the Explorers Club.

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