Ask Jill: Rebreather Diving Antarctica

Question:

I’d like to ask whether you had any problems diving in Antarctica with a rebreather?
I’m planning an underwater photography trip there myself with a Megalodon and wonder if there are any problems with the cold. I have the 8lb radial canister.
Apart from spare batteries, do I have to watch out for anything apart from always keeping the unit warm and adequately pre-breathing?
Thanks,
Marcus

Answer:

Hi Marcus,

Thanks for your note. You will love diving the rebreather in Antarctica. It will definitely keep you much warmer than OC. We did not experience any free flows on the first stages since there is very little demand for high volumes of gas passing through the first stages. Be careful with your OC bail out bottles and do not breathe them wet in the surface conditions. The chill in the topside air is often enough to trigger a free flow. Check only once submerged and do it gently! In the event that you ever bail to open circuit, remember that the gas passing through the first stage is the water temp, which can be near or even below zero centigrade. Stagger inhalations and other additions of gas like dry suits or wings and keep your breathing rate relaxed. In the event of a free flow, be prepared to shut down and switch to something else while the first stage thaws.

Batteries get eaten up quickly in the cold, so have lots of hand warmers close by for cameras etc. Pre-breathe your loop early and long to start the exothermic reaction in the canister and keep the head and batteries warm. Consider insulating the stack or breathing loop if you want longer durations, otherwise be very conservative with stack time.

After diving, get everything as dry as possible. You may even need to take apart things like the manual addition valves into the counterlungs. If you leave them wet and they freeze, they will likely stick open or closed when you go to dive. Although they will eventually thaw underwater, it takes more time that you might be used to due to the hyper-cold salt water. The last thing you want is a stuck closed ADV when you have just rolled off the boat for a descent!

Finally, keep a close eye on o-ring seals. In the topside chill, anything with an o-ring could start leaking as it gets harder. Frankly, once you are underwater, everything is awesome. It is the topside conditions and the very beginning of the dive that will get your gear and your body.

Have a great trip and send us some shots for RebreatherPro. I'm sure others would love to follow your trip!  Jill Heinerth

Comments

[Erik]

is that a Bail Out Rebreather on your left side? What RB did you dive in Antartica ? Your meg ?

[Jill]

That was actually a massive HID light that we had engineered specifically for the project by Barry Miller. Technology has come a long way since then, but its such a great light, we just dropped it off yesterday for a rebuild.
I was diving the Cis-Lunar MK-5P rebreather built by Dr. Bill Stone.