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Sci-tech: Self-contained underwater breathing apparatus, or how to be a fish underwater
Published in Daily News Egypt on 23 - 12 - 2006


Respect your body, your equipment, and the Red Sea
Egypt has been blessed with the Red Sea; you can swim in its warm waters, surf its windy swells, or dive its stunning depths. And in attempting to do the latter in bodies of water the world over, we humans have uncovered a life much less ordinary.
Freediving, which relies only on breath-holding, has been around since humanity began. Diving with an air supply likely started with long reeds, the predecessor to the snorkel, but any longer than a meter and it becomes too difficult to breathe against the water pressure.
From the late 1700s to the mid 1900s, various European inventors experimented with improvements to air supply, first manually pumped from the surface and then later becoming self-contained. And as many of us remember from childhood schooling, it was Jacques Cousteau's aqua lung which was the considered the brilliant foundation of today's scuba gear.
If you've been snorkeling already, and intend to again, then you should start buying your own gear, so when the time comes to take the plunge, you're good to go.
A mask and snorkel are a good place to start. A comfortable mask that fits the shape of your face can be hard to find, but once you find it, buy one. Consider splashing out on a snorkel with a closure valve that seals against water, so you don't end up gasping on the pounding waves that could otherwise be sent through your snorkel by the blustery winds of a Red Sea in winter or spring.
Fins are considerably more straightforward, and your best bet is a pair of open-footed ones that you use with a pair of neoprene booties, enabling you to then traipse more comfortably over the reef.
Your remaining equipment - high-pressure tanks holding compressed air, a regulator that supplies air at the correct pressure, a buoyancy vest to be inflated or deflated via your air tanks, and a wet suit - can all be hired from the nearest dive center.
Once you have assembled all this kit, you're ready to swim with the fishes - but not in the mafia sense, so listen up.
As you descend into the shark-laden depths, the squeals you hear may not be due to toothy predators, but rather the reaction of your inner ears to pressure changes. As with chewing bubblegum as an airplane drops altitude to land, blowing gently against a pinched nose can help you equalize the pressure as you descend below the water's surface.
As you go down, the air inside your ears becomes compressed from the extra weight of the atmosphere and the water above, increasing the pressure all around you. The pressure difference should be equalized every meter, or the resulting ruptured eardrum will not just stop you diving for the next while - it will hurt like hell.
As for your breathing apparatus and its air: Oxygen, under pressure, will become toxic - at just over 10 meters if breathing pure oxygen, and at 105 meters if breathing air. This demands that the percentage of oxygen in your tanks be decreased for deeper dives.
Keep in mind that air consists of both nitrogen and oxygen. And as nearly 80 percent is nitrogen, this is the gas that should concern you most while diving. When descending, the increased pressure compresses the body, causing the nitrogen to be intensively absorbed by the blood and dissolved, meaning nitrogen narcosis and its resulting disorientation and feeling of intoxication.
When rising back to the surface, decompression occurs and the ensuing pressure decrease releases the nitrogen gas from the cells and tissues. If the diver ascends too fast, before complete desaturation takes place, nitrogen forms bubbles in the cells and tissues; these dangerous bubbles can plug small arteries and stop the flow of blood to the organs.
Decompression tables, or a dive computer, will tell you how long you can safely stay at a certain depth, and how to safely ascend from various depths with differing durations and breathing mixtures.
Given the difficulties and risks of diving, some may wonder why anyone would go to all this trouble in the first place.
While 'returning to the womb' maybe an over simplification, or exaggeration, of the feeling of breathing underwater, being in such an environment can indeed connect you with positive and powerful emotions. The underwater world can be humbling and affect your view on life itself.
As you emerge from the deep and are walking out from the Red Sea, you might even be so moved as to find yourself collecting some of the many plastic carrier bags that sadly litter so much of the coastline.
Before you get too carried away though with a sense of oneness with your sub-marine brethren, it's best to keep a respectful distance from them - do not touch the fish, or anything in fact. After all, many underwater creatures are masters of disguise, and self-defense, and by the time you realize that spectacular plant is actually a venomous lionfish - "but it's so pwetty . uh . nnngh . aaargh! is all that will follow after its hypodermic needle-like dorsal spines inject you with neurotoxin.
Not that I hold anything against the sea urchin that impaled my hand at 18 m .


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