March 4, 2016
Written by: Sophie Gaze
Dive Immersion Senior Divemaster
The next phase of our rebreather training took place in the safety of a pool at Cobb Aquatic Center. We loaded up the Georgia Aquarium van and eagerly made our way up north to the facility. The time had come for us to finally get our heads under water with this new equipment on our backs!
The pool was truly like a playground for us. In any type of dive training, there is a great educational benefit to training in a pool. In this case, it allowed us to gain confidence handling the equipment, running through the tests and practicing our buoyancy in the water. There, we also had a false sense of security training in the shallow, crystal clear water of Cobb Aquatic Center – something we knew we should not get used to, given that the rest of our training would be the murky, spooky waters of Lake Lanier or the absolutely frigid Dive Georgia Quarry.
We began our pool training by practicing running through the tests on our rebreathers. Poseidon SE7EN rebreathers run through a series of 55 automated and semi-automated tests to confirm that all necessary mechanisms of the equipment are in working order. After the final test, a five-minute pre-breathe is required before using the equipment. The purpose of the pre-breathe is to track the diver’s metabolic rate and check the function of the oxygen addition system, so it is a very important step to get used to completing before entering the water.
The most important in-water skill we practiced was establishing minimum loop volume (MLV). This allows the diver to take a full breath from the counterlung without triggering the rebreather system to add any additional diluent to your breathing loop. This, in addition to proper weighting, is also the first step to mastering good buoyancy in a rebreather unit.
After we had practiced establishing MLV, we were able to swim around and get used to breathing with the new units. One of the biggest challenges for new rebreather divers who are used to open circuit SCUBA is maintaining buoyancy. On open circuit, an exhale caused the diver to descend in the water column, and an inhale causes the diver to ascend. On a rebreather, the dynamic is the complete opposite, so it is very strange at first for someone accustomed to open circuit. This took a while to get used to, but once I did, I found that I really enjoyed the relaxing silence of the rebreather unit. It was very calming to be surrounded by water and breathing so naturally even though the equipment was new to me. I instantly understood why this new Closed-Circuit Rebreather Dive Program would be a hit with our dive guests at Georgia Aquarium!
Once we felt we had mastered control of our buoyancy, we also performed drills with our SSAA’s, or “safe second alternate air source.” This was important because when we eventually dive in the field, we will need to have an SSAA attached to us for two reasons: to serve as a bail-out in the event that we run out of diluent, and to use as a gas source to fill our dry suits with air. In the pool, we practiced switching from our rebreather regulator to our SSAA regulator, as well as handing off our SSAA to another diver in the event they needed to breathe from it.
After a long day at the pool completing our confined water dives, we were ready to give the units a go in Ocean Voyager Built by The Home Depot. This was something we were all really looking forward to, because we had been taught that the animals would approach us much more willingly without the noisy bubbles from an open circuit system. We were also excited to start clocking hours on the unit in a body of water larger than a 12-foot pool!