By Annabel Thomas
For The Bali Times
SEMINYAK ~ Go placidly amid the noise and haste, and remember what peace there may be in silence*
There cannot be a scuba diver who has not wondered how it would be to dive bubble-free, without the sound (albeit reassuring sound!) of the air passing in and out of the second stage of your regulator; to be silently, naturally, moving through the sea … just as our ancestors did oh so many years ago.
It is actually possible to dive with a piece of equipment, called a rebreather, that will enable you to do just that. Of course it takes special training and there are life-preserving rules that are vital to follow.
But first, the basics: As you inhale, your body uses the oxygen and produces carbon dioxide. A diver using standard SCUBA (open-circuit) equipment will use only 25 percent of the oxygen breathed in; the rest is exhaled into the water along with the carbon dioxide and nitrogen in the breathed air. A rebreather recycles that exhaled air (no bubbles â€“ i.e. closed-circuit): absorbing the carbon dioxide and adding oxygen to replace what has already been used up. This reduces the amount of gas that a diver needs to take diving, meaning a rebreather is also lighter and more compact than a standard SCUBA unit.
Due to increased pressure on the body, the deeper a diver goes, the higher the amount of oxygen breathed in. Oxygen can actually be toxic if breathed at too high a concentration – hence recreational divers being certified to a maximum depth of 30 meters and the advice to not dive deeper than 40 meters. To dive to 60 meters on normal compressed air means you risk oxygen toxicity … however, as rebreathers have the capacity to reduce the percentage of oxygen, they can be used to greater depths.
There is also a â€œsemi-closedâ€ rebreather which produces some, but fewer, bubbles than SCUBA systems.
It is believed that the first rebreather (albeit very basic) was made in the 1620s as part of an oar-powered submarine. In the late 19th century, there were a few different rebreathers available but they were used for purposes such as mine rescues where it was believed there may be toxic gases present. Later they were used to escape from sunken submarines but were perhaps most notoriously used by Italian navy frogmen during World War II.
These days, diving rebreathers, although expensive, are found all over the world. The lack of bubbles (and therefore reduced noise) enables military divers to move around in greater secrecy. For underwater photographers and videographers and marine biologists, this simply means they can get closer to their subjects. Obviously rebreathers are safer when exploring deep cave systems and wrecks, due to the fact that oxygen percentages can be changed, and also thereâ€™s less chance of running out of breathable gas either due to the length of time needed for ascents and descents – and if you have the misfortune to get lost or entangled.
Here in Indonesia, thereâ€™s only one company that offers rebreather courses/training, rebreather dives and rebreather rentals and sales: Blue Marlin Diving in Lombok (www.bluemarlindive.com/technical_diving.php).
Desiderata, Â© Max Ehrmann, 1952
The writer is director of AquaMarine Diving â€“ BaliFiled under: The Island