Rebreathers: Just A Little Bi Curious
Rebreathers: Just A Little Bi Curious by Greg Wilkinson
I'm 30m underwater, I've been down for over an hour. Still got loads of gas left. It's warm, vis is great, fish are swimming right up to me. And I've not got any bubbles! None! I've been learning how to use the JJ rebreather with Alan at TechWise in Malta and I have to say, it is AWESOME!
The course covers all you need to know to get to grips with diving a rebreather. There's some theory to cover and lots of in water practice. The unit is assembled with the aid of a checklist to ensure you set it up properly. It isn't difficult but it definitely works better when everything is assembled properly. Gas cylinders need to be checked before use. A rebreather uses pure oxygen and another gas to dilute the oxygen to a safe level.
On my course air was used as the diluent which means I was breathing a nitrox mix during the dive. A rebreather maintains a constant oxygen partial pressure so the actual nitrox mix changes with depth, which means decompression becomes more efficient compared to open circuit. Pre dive buddy checks help confirm everything is working properly before you jump in the water.
The training focuses on helping you understand how the unit works and how to take control of all the functions manually should the need arise. You also get to learn lots of cool new terms such as ADV, DSV, MAV and set points.
How It Feels
Wearing the unit in the water feels pretty much like wearing a twinset. And if you've never used a twinset, it feels like a solid, compact unit sitting comfortably on your back. One big difference though is buoyancy control. On open circuit when you breathe out you sink a bit and when you breathe in you float a bit. On a closed circuit rebreather that doesn't happen, you just move the gas from your lungs to the units counter lungs with no change in buoyancy. It took me a few dives to get used to that. Many times I landed on the seabed in a cloud of sand!
So, what made me want to dive on a rebreather? Well, I'd read about all the advantages such as more efficient gas use, more time in the water, no bubbles, quieter diving, getting closer to the fishes etc, but at the end of the day I guess I was just a little bi-curious and wanted to try it for myself, plus it just looked that bit more......frogman!
Diving The JJ Rebreather
And so there I was, at Cirkewa, swimming from the wreck of the Rozi to the P29. Normally done as two dives, the extra duration gained by using a rebreather means they can be combined into a single dive. I follow Alan under the hull, he stops on the far side, turns around to film us on his GoPro. I get in trim, check my position, just off the sandy seabed, feeling good, I look casually past the camera and swim slap bang into the hull. The clang of metal hitting my unit is only drowned out by the sound of my laughing! Oh well, not perfect just yet. But there's always the next dive. Bring it on!
By Greg Wilkinson
PADI Master Instructor, JJ CCR Diver, OC Trimix Diver
Follow the links below to find out more about becoming a Rebreather diver!
The Tec 40 CCR course is your entry into the tec diving realm. Learn the details of proper setup, predive checks, dive planning, failure and problem management and teamwork for CCR diving.