Why I Switched from Diving Sidemount to CCR

By Chuck Eddy

Although I’m from Minnesota, my first scuba diving experiences were all in Asia. While living and working in China, I was fortunate to have been able to take yearly vacations to several islands in Thailand during Chinese New Year, adding new scuba certifications each visit. By the time I moved back to Minnesota in 2010, I was a Divemaster, but had never known anything beyond single tank diving wearing a 3mm shorty. Back in the US, I was surprised to discover the incredible shipwreck diving available right in my home state. While I thoroughly enjoyed seeing whale sharks and manta rays in Asian waters, I became intrigued by the many shipwrecks spread throughout the nearby Great Lakes. All it took was one dive wearing a 7mm wetsuit in Lake Superior’s 36°F water to convince me to purchase a drysuit. 

After becoming an Open Water Instructor in 2011, I logged many cold and warm water dives using a variety of tanks; steel 72s, 80s, 85s, 108s and aluminum 80s. Yet, I began to become dissatisfied with the length of dive time at depth I was getting out of my single tank set-up. In 2014, at the suggestion of a friend, I tried out a two-tank sidemount set-up at a local mine pit and absolutely loved it. Having a tank on each side with its own regulator and pressure gauge felt so much safer and more natural to me than having a big, fat steel 108 strapped to my back. 

Once you go sidemount you don’t go back 

Soon afterward, I purchased my own sidemount gear and began diving sidemount almost exclusively. After watching videos of sidemount practitioners, some of whom were diving up to 8 tanks at a time, I was inspired to get my buoyancy and trim dialed in with each set of tanks I owned. Following the completion of the Advanced Nitrox and Deco Procedures courses, I began doing decompression diving with up to 4 tanks at a time. The following year I became Full Cave certified. 

Overall, I marveled at the versatility of my sidemount gear configuration, as it allowed me to penetrate tight spaces in shipwrecks and caves that some of my dive buddies couldn’t fit into. In addition, sidemount easily allows one to don and doff tanks underwater, clip them off on a line or outside a shipwreck, or stage tanks for cave diving. By 2018, with over 230 sidemount dives, I had grown very accustomed to my 2-4 tank sidemount set up. I was so stoked about sidemount diving that I even bought a t-shirt that said: “Once You Go Sidemount You Never Go Back”.

And then you’re “that guy” 

Yet, despite my sidemount system performing amazing while in the water, the one context I found it to be both awkward and inconvenient in was cold water boat diving. It was only with considerable planning, effort, and practice that I was able to get off and back onto a boat in a drysuit with 2-3 side mounted tanks and camera gear in a timely fashion that could compare to what back-mounted divers were doing with ease. Having to take up more space than others on a charter, to drop tanks on a line or drag them over the boat’s railings, and to endure the grimaces of captains and deckhands as they assist you in and out of the water, fretfully eyeing you to make sure you don’t damage their vessel with your dangling tanks, all began to get old to me. Thus, I’ve not yet met a Great Lakes boat captain who was overjoyed to host sidemount divers on their charter. Beyond these issues, due to the added task of loading sidemount set-ups, I’ve watched sidemount divers on charters end up delaying everyone else from getting into and out of the water. Nobody wants to be “that guy”.

Then there’s cave diving 

However, it was my experience during the 2nd cave dive of the day at Roubidoux Springs in Waynesville, MO that proved to be the turning point which moved me a step closer to getting a closed-circuit rebreather. Although this was my buddy’s and my first dive trip to this spring, we were able to secure a decent map of the cave, and using dive planning software, I was able to accurately plan my gas usage. The limiting factor on this dive was my open circuit gas consumption. I was diving air, using two heavy steel 108s and an aluminum 40 with 82% O2. My buddy was diving a Megalodon closed circuit rebreather. 

The water temperature was 59°F, which is considered warm by Minnesota standards, and being a spring with light outflow, the visibility was excellent, often exceeding 50 feet at depth. The cave by the way, is fascinating, with sloping hills, valleys and the type of rock formations that are only visible in such an environment. There was also a school of Trout and many other fish greeting us as we entered…anyway… 

Open vs. closed 

Our max depth had been 145ft, and we spent approximately 20 minutes at this depth, turning the dive when I had consumed 1/3 of my gas. Knowing that we would spend 20 minutes at 145 feet, we had planned this as a decompression dive. However, I was somewhat taken aback when I when fully realized the difference in the decompression commitment between my buddy and me. After we turned the dive and proceeded out of the cave, I had 30 minutes of decompression I had to complete before I could get out of the water, making my dive 71 minutes long in total. My CCR diving buddy on the other hand, only had 3 minutes decompression and exited 20 minutes before I did. 

Why this vast difference? 

I could have dove a mixture of Nitrox 26% which would have eased my decompression commitment by a few minutes. However, the primary difference is due to the fact that a closed-circuit rebreather has the ability to optimize the oxygen in one’s breathing loop at all times. So, my buddy was able to dive an oxygen rich Nitrox mixture of gas throughout the totality both of our dives. Thus, reducing his decompression commitment considerably. It was this experience that launched me into a period of serious investigation into the other advantages of rebreather diving. 

What I discovered was, rebreathers, with their much lower gas consumption, provide for vastly longer dive times and thus significantly reduce the primary safety risk of cave and wreck penetration diving on open circuit; running out of air. For cold water diving, a rebreather also reduces one’s thermal loss by recycling one’s own warm breath, in contrast to open circuit diving where each breath is drawn from a cold tank, chilled by the ambient water temperature. While the initial cost of a rebreather can seem steep, for anyone who dives regularly it’s a great investment as the overall usage and costs of air/gas become far less than those of open circuit. This is markedly noticeable with mixed gas diving, as it is far cheaper to fill a 3-liter rebreather tank with trimix than to do so with a twin set of steel 85s or aluminum 80s. 

Making the switch 

All these factors propelled me to try several rebreathers and ultimately settle on a rEvo Micro III, which honestly seemed to say “Yes!” to me when I demo-ed it for an hour in the pool. Yet, after diving open-circuit for many years, I have to confess that learning to dive a rebreather is definitely challenging as at times it can feel like learning to dive all over again. You have to learn how to manage the airspace of the counterlungs and the loop without the use of your breath to control your buoyancy. I’m grateful to have had a world class rebreather instructor who lives nearby to train me on my unit. By no means did he hand me the certification. I had to show him that I had mastered all the bailout and safety skills sufficiently before he would certify me. I observed that the demands of rebreather training exceeded those of most of the technical scuba courses I have done so far.  

Silent Operation 

Finally, another considerable benefit of diving rebreathers is their silent operation. After going through the first level training, developing the skills, and putting hours on my rebreather in lakes, mine pits, and caves. I began to notice that fish no longer flee in my presence, as was the case when I was diving open-circuit, but rather will cautiously approach me. Besides the obvious advantage this has for underwater photography and videography, the zen-like quiet in which one only hears their own breath underwater provides an added dimension of relaxation, peace and tranquility to diving. Overall, as I continue to focus on gaining more time and skills on my unit, I have to say I’m very happy to have made the switch from diving open-circuit sidemount to CCR. While I still plan to dive side mount in certain types of settings, for the time being I’m very focused on mastering CCR.

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