Rebreather

The rebreather has been around for a long time, and was used extensively by Navy ‘frogmen’ during wartime. It was used for several reasons, the most important being it was the only game in town. It had the military advantage of being totally silent and bubble free lending itself to much needed stealth in wartime and battle conditions. These, of course, were sealed  or ‘closed’ units using pure oxygen, and if you were to venture by accident or possibly need to avoid the enemy below the magic 33 foot depth you found yourself suddenly  and permanently quite dead!

Needless to say, things have changed over the years, and the modern rebreather is a much more sophisticated and safe device. They now come in two basic formats - closed and semi closed. The closed units are still very difficult to use and inheriently still fairly dangerous even in well trained hands. These truly cannot be considered ‘sport’ units. The semi closed devices, however, are relatively simple and straight forward in design and use.

To the left you can see the main difference between the closed and semi closed units. The semi closed unit does exhale a small amount of bubbles occassionally. This is because you do not fully reuse all the air in the system and, as excess air builds up in the breathing bag, it is sporatically vented as the pressure builds to a preset limit. This, along with the ability to remain submerged for up to 3 hours on one tank makes it a wonderful photographic tool. Even when it does vent, it is more of a suppressed gurgle than the constant roar of scuba.

During this test, I was able to use the unit in depths ranging from 35 feet to a max of 100 feet. The photos on this page are all taken at 65 feet on a wall in Roatan, Honduras. Due to problems with the nitrox mix I was able to get, I only managed 2 hours per fill or two dives compared with one scuba diver on each tank. With the proper mix, you can easily take the unit out on a three tank boat dive with no fear of running out of air. Bear in mind that, unlike scuba, depth has no bearing on gas usage. You have the same amount of time per tank regardless of depth.

Some of this sounds too good to be true - right! Well, obviously, nothing is all good. There are some negatives to anything, and rebreathers are no exception. These units are very bulky and heavy on land. Walking around the dock is no cakewalk, not to mention getting over the sides of a boat to enter the water. However, even with this the unit is very well balanced to carry even out of the water. As to getting into the water from the boat, I found the ‘giant stride’ to be the only acceptable method. Also, transportation is a major issue, as the units take up over half your baggae weight allowance on most airlines. If you carry the rebreather and photo equipment, you better be great at packing or expect surcharges for over weight. Probably the biggest drawback to the rebreather, unfortunately, is the one I least expected. There is just no support for nitrox gas out there as yet. I thought by now nitrox was available anywhere, but soon discovered (after hauling gear all over the Caribbean) that few places actually have it, and the few that do have serious supply and quality control problems. And, of course, don’t forget this is still technical diving. One of the hazards to this type unit is carrying a caustic substance (soda lime) around and breathing throughit. If you let any water leak into the air supply, you get a very nasty reaction from the soda which can burn your mouth and lungs if you allow it to get that far. For this reason, the unit comes with an emergency bailout bottle to get you home. I have talked to divers who have experienced this, and, while not fatal, it is a very unfriendly episode. Even if all you do is get a few fumes, it can make you extremely nausious and ill for several hours.There’s a lot more work to diving rebreathers. Your dive must be planned well, and there is a lot more work involved both pre and post dive in caring for, prepping, and cleaning the equipment.

Don’t forget, this takes specialized training and a rebreather certification. I have one complaint about the Drager equipment, and, in fact, it isn’t really about the equipment. It is crucial that you seek out good qualified instruction. The unit is very straightforward and simple - yes. However, that’s once you understand it’s functioning. The manual that comes with the unit will get you killed. It is possibly one of the worst detailed and written manuals I have ever seen. The manual apparently presupposes you already are a rebreather expert, in which case you did’t need it anyway. Even after going through training, the manual will confuse rather than help. Drager really needs to get their act together on this. And why not, they did a great job on the equipment.

So, about now you gotta be saying to yourself ‘Why would I want to do this?”. I would have to say that I wish it was all I had to dive with. Despite the extra work and problems, it is a great way to dive. The Drager unit is extremely well designed. It is very well thought out and easy to service, assemble, clean, and maintain. The process of learning the gear is not a lot different from learning nitrox diving (A certification you must have first by the way.). In the water, the Drager unit is quite comfortable. I found it much more comfortable than the standard scuba tank banging around behind. You get one other unique advantage with rebreathers as well. You are breathing warm moist air instead of the cold dry air of scuba. There are two big advantages to this. First, the moist air doesn’t give you that wonderful dry mouth and throat sensation as does scuba. Secondly, the warm air doesn’t chill your body and you stay warmer during the dive, so you don’t end up with the shivers and muscle soreness after each dive.

And, of course, when all is said and done, there is that wonderful advantage of being able to stay down seemingly forever.