The Silent World of Rebreather Diving

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I remember the day clearly, it was overcast and raining and there was no diving in Puerto. A chance glance through a magazine and an innocent question.

“Dave, do you do a discover rebreather course?”

“Yeah sure, next week okay?”

“Done” I said.

And so began a journey into the silent world of rebreather diving. This article is a reflection on the best years diving I’ve ever had and maybe a few pointers for others who may be thinking of embarking on the same route.

My first steps began using the Draeger Dolphin unit. It’s a semi-closed system that relies on a premixed Nitrox tank to deliver gas into the breathing loop. Draeger have been building breathing systems for years and this was their first attempt at the sport diver market and I couldn’t wait to get in the water. My first ever rebreather dive was off the beach in Small La Laguna and once I’d got used to the silence and spent 20 minutes bouncing off the bottom because your open circuit buoyancy skills don’t work any more, I settled down next to a small piece of coral. It was so much fun I could not stop laughing when I realised that the piece of coral I normally just swam over was teeming with more life than I ever imagined. The complete silence, except for the faint sound of some bubbles behind my head, and the total lack of exhaust bubbles made it seem like my first ever dive again. Things progressed nicely and I clocked up about 20 hours on the Dolphin with some memorable dives in the Canyons. Two divers on breathers, swirling jacks and eddies in the Second Canyons and no one else around. Even better was a 5:30 am drop in to Canyons to see it spring to life. It was fantastic.

A quick trip to the Sulu Sea on the Tabibuga on open circuit convinced me that rebreathers were the way I wanted to go. The thought of not being able to swim ‘with’ fish rather than watch them was just too tempting. I looked around and selected the Buddy Inspiration Closed Circuit Rebreather. This unit is also aimed at the sport diver market and differed from the Dolphin in that it is electronically controlled and maintains a constant partial pressure of oxygen at any depth. In fact its a ‘blendo-matic’ as it mixes the appropriate percentage of oxygen for the depth you are at. You do need to have done basic technical training before using an Inspiration, but only a Nitrox course for the Dolphin. The technical training is a sensible route to take as any closed circuit rebreather is more complex than open circuit and requires a higher skill and confidence level.

After completing the course I dove the hell out it for 6 months, gradually building up experience and confidence in its basic operation. The system is very simple to use and the electronics work well. So well in fact that there’s a temptation to progress much faster onto deeper and longer dives. It sometimes felt that I was missing new experiences by going slowly, but with hindsight I’m really glad I progressed slowly and methodically in building up in water time. One of the common threads to come out of analysing rebreather fatalities has been people pushing themselves too fast, going too deep too soon, or undertaking challenging dives too quickly after training.

The other main cause of problems is getting complacent and not performing the required pre dive drills and maintenance that MUST be done in a methodical way. Open circuit gear is very robust and takes a fair amount of abuse. Rebreathers cannot be treated this way, they must be meticulously prepared and checked before each dive. It can be tempting to skip a check in order to hurry into the water, this must be avoided by getting into a meticulous routine of pre dive and post dive checks. A Nobel Prize wining physicist did not turn his oxygen tank on and died in shallow water, so if it can happen to him, it can happen to anyone if you don’t develop a systematic routine. This is another reason for progressing slowly in the early days.

Last Christmas I took the technical rebreather course which shows you how to undertake deeper dives with helium in the loop. Its on the deeper dives that you get more benefits of using a rebreather. I was getting 3 trimix dives from a 3 litre cylinder so helium costs are negligible, constant partial pressure of oxygen throughout the dive gave shorter decompression times and not having to worry about your RMV and therefore gas consumption made swimming at depth a joy. You do however have to be in the groove and know what the rebreather is doing by constantly watching your PO2.

Next year I’ll be taking it to Guam and Truk Lagoon for a deep week on the Aggressor. The abundant fish life and no bubbles will reduce silting on the wrecks and should provide another memorable experience.

What thoughts do I have for anyone thinking of diving a rebreather?

Start slowly and start simply.

Learn on a semi-closed system such as the Dolphin or Ray and build up at least 20 hours on those units first. This will allow you to decide if you want to make the further investment in time and money to progress further, or are just happy to stay shallower than 30m and use rental units of which there are many in the Philippines now.

Find an experienced instructor and avoid discount courses. Rebreathers are new pieces of kit and experienced instructors in these early days are quite rare. Ask your potential instructor how many people they’ve trained and then ask their old students for a second opinion, also find out how often they dive the units themselves. You get what you pay for and a good experienced instructor will also impart their practical experience in addition to the course. Personally I can recommend Dave Ross of Asia Divers for the Dolphin, and Paul Nielsen of Mandarin Divers in Hong Kong for just about any rebreather currently on the market.

Ask yourself honestly if your the right type of person to dive a rebreather? I’m not a psychologist, but I’d ask myself a few simple questions such as:

Have I ever got in a dive boat without my mask and fins?
Do I wear a seat belt for long journeys only, but not wear one if its only 5 min trip down the road?
When tempted to push a dive because its a great dive, did you push it?
Have I ever jumped in with my air turned off?
Do I never practice basic skills when diving such as mask removal etc?

If you answered yes to more than one of these questions then my advice would be to become more methodical and responsible in OC diving before moving onto a rebreather. To my knowledge over 99% of rebreather accidents have been put down to diver error through pushing the limits or not doing the pre dive checks and maintenance.

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