Once in the pool, we reviewed a few basics on the surface, and dropped down to the deep end, in 10 FCW. (Feet of Chlorinated Water.) We started to swim in a square pattern, doing a different drill in each corner; and getting a bit more familiar with our units at the same time. (Revelation: As you ascend on a closed loop, you must vent gas through your nose as the loop volume expands!) The drills teach you to deal with what Rebreather divers call the 3 “Hs”: Hypercapnia, (Carbon Dioxide in the loop), Hyperoxia, (Too much oxygen in the loop), and Hypoxia (Too little oxygen in the loop.) Any of these 3 conditions is to be considered an emergency, and must be dealt with immediately! Mel taught us how to execute an “Open Loop Diluent Flush,” Which we would be doing many, many, times before the class was over! This procedure floods the entire breathing loop with gas from the diluent tank on the diver’s back, which is breathable at any depth during the dive. The idea is to build muscle memory, and make our responses to emergency situations automatic, and it really works! One huge difference between diving open-circuit and diving closed circuit is that the breathing gas in the loop is dynamic, or ever-changing. It’s up to the individual diver to monitor the gas, and make changes as necessary. The other drills we learned (over and over and over again!) were loop recovery- what to do if the breathing loop, (called the DSV, for “Dive Surface Valve” in CCR terminology) becomes dislodged from the diver’s mouth at any time, and the infamous “Boom Drill.” Since we’re diving with 19 cf tanks of oxygen and diluent, any gas loss can deplete our supply in seconds, so it has to be dealt with immediately. The diver reaches back and twists the valves closed as quickly as possible, then grabs his or her gauges, and tries to determine which side the leak is coming from, finishing by checking the pp02 level in the loop to see if there was an “internal boom.”. During this time, I ended up kneeling on the bottom of the pool next to Calvin, waiting for a “traffic jam” to clear up in front of us. I turned towards him and said, through the mouthpiece of my DSV, “Can you hear me?” He looked back at me and said “Yeah! I can hear you fine!” It was pretty cool- we started jabbering at each other for a few minutes, until we could move on. We found out the next day that we couldn’t hear each other as well with the thick hoods us cold water divers wear in open water, but it still works better than open circuit! After adding our bailout tanks to the drill menu, and practicing open circuit bailouts, we got out of the pool and headed back to HQ.
Back at the dive locker, we took our CCRs apart, following a comprehensive checklist provided by the manufacturer, and, equally important, guided by Mel, who patiently answered all of our many questions, and showed us dozens of tips and tricks for working on our units, such as how to avoid pinching O rings while assembling the DSV, and how to test and replace batteries. Her extensive experience with CCRs in general, and Megalodons in particular, was clearly in evidence throughout the entire class. She is an excellent teacher, and her passion for rebreathers is contagious. Then, it was off to the classroom for lectures and bookwork.
Meg head removed from unit
DSV and loop
Calvin assembles his Meg
Curt had dinner ready for us around 5 pm, and we took a much needed break back at the house. After dinner, we went back to the dive locker, and assembled and “pre-dived” our Megs, finishing up at 7 pm- an “early night!”
The next day started at 7 am, down at Alki Cove 2- a site familiar to all of us Seattle divers! We did 3 dives this day, and all of us learned that our buoyancy characteristics on closed circuit are quite different than we were used to on open circuit! Nobody “corked” to the surface, but I know every on of the students had a “special” moment of thrashing around, trying to vent their dry suit, or pushing off the bottom…. But, really, after all I had read about how hard it was to make this transition, it wasn’t that bad. Once you come to terms with the fact that you can inhale all you want, and you won’t rise an inch, you start to deal with your new reality. And what a reality! I have done the dive profiles that we did in class many, many, times…..but they seemed completely different, somehow. I had heard that one could approach fish much closer on Closed Circuit than on Open Circuit…..and it’s true. Larry said he felt like he was watching a movie with the sound off, and I felt like that, too. But it’s more than that- once we settled into our rigs a little bit, it was incredibly peaceful. There’s something else about diving closed circuit that I can’t put my finger on, exactly, but I really like it. And the “No Deco” times are incredible! We are breathing an ideal mix of Nitrox at every depth, giving us greatly extended bottom times, as compared to open circuit. We finished up the 3 dives relatively uneventfully, except that one of the students started to get too much water in his breathing loop on the last dive, and elected to bail out on open circuit. This was a little bit exciting, but everybody handled it well, and we had more than enough bailout gas, so it wasn’t an emergency by any stretch of the imagination. On shore, we did a post dive briefing, and then headed back to the shop to take apart our units, have more lectures, eat a huge dinner, re assemble our units, and finish up around 9 PM- and this was our pattern for the next few days- sleep, dive, post dive, lectures, eat, pre dive, and sleep!
Me, Mel, Calvin, Dan, and Larry (left to right)
By Saturday, the 16th, we were all feeling much more confident assembling our Megs, packing our scrubbers, doing our checklists, buddy checks, and post dives. We did our final 2 class dives, reviewed the exams we had taken on Friday, and went out for a graduation party. I’m a little hazy on the details, but I’ve been told that I had a great time!
The Party!
All of us students are now officially raw, green, Rebreather divers, and we have much to learn, yet. I’ve read elsewhere about the difference between experience and training, and I’ve found that difference for myself at a few junctures during my open circuit training and diving. We have been given excellent training, and now we need to rack up some hours on our Megs, and I can’t wait! A huge “Thank You!” to Mel and Curt for the training and hospitality, and to Greg for leading the dives!
Me, Looking smug!
I couldn't quite figure out how many days or dives you were out there? 
