SCUBA is an acronym standing for Self-Contained Underwater Breathing Apparatus. So it's really a noun, not an adjective, describing the air tank and the bits and pieces attached to it.
Scuba diving theory
Never having tried scuba diving before, I decided to sign up for a one-day introductory course with the Underwater Centre adjoining the Coral Strand hotel, on Beau Vallon Beach (the longest and most popular beach in the north of Mahé).
This was within 5 km of my hotel, so I walked down in the morning, arriving in time for the 9:30 start.
There were six of us, all men: two Germans, a Swiss, a Frenchman, a South African, and me. The South African looked older than me, the others younger. Our instructor was a young German lady from Dortmund, called Suzanne, who told us candidly that she'd been in the Seychelles for only six weeks, and was working as a nurse before that (in Australia, I think). However, she was patient and careful, and seemed to know what she was doing.
She spoke to us in good English, that being the only common language of the whole group, though she gave further explanations in German from time to time if the German-speakers had trouble following her in English.
The first stage was to sit us around a table and give us a long lecture, with diagrams, on the theory of diving, the effects of water pressure on the body, the use of the equipment, and the various conventional signals used for underwater communication.
Then we got into partial wetsuits (not covering the legs and arms) and all the other gear, and staggered off to the nearby swimming pool of the Coral Strand hotel. On top of the wetsuit, you wear an inflatable jacket to which the air tank is attached, along with various hoses and gauges, and a belt with weights to cancel your natural buoyancy. Then there are the mask and flippers — which Suzanne called “fins”. After my holiday, I bought a book on scuba diving, and found that it also refers to “fins”; I suppose this must be the modern fashion.
The air tank weighs a ton. In the water, you don't notice it, but out of water it's a heavy burden.
We stood in the shallow end of the swimming pool, feeling somewhat ridiculous; the sunbathers looked on curiously. After some further instruction, we put on our masks, put in our mouthpieces and knelt cautiously on the bottom to try using the equipment under water for the first time. We practised half-filling our masks with water and then expelling the water by breathing out through our noses. We practised losing and recovering our mouthpieces under water. Then we swam slowly around the pool, under water.
After this exercise, we returned to the Centre, removed our gear, and took a lunch break (I ate at the Coral Strand's poolside bistro).
Scuba diving practice
In the afternoon we were taken out on a fast boat to one of the nearby areas of coral, where we were to dive. One of the Germans was no longer with us: either he or Suzanne had decided that it was not a good idea for him to continue.
As instructed, we solemnly spat in our masks and then rinsed them in the sea before putting them on; this apparently makes for clear vision, preventing them from misting up. Then, one at a time, we fell backwards into the sea off the side of the boat, and gathered around the bow.
The inflatable jacket may be inflated at the press of a button, using the air tank; or deflated at the press of another button. We entered the water with our jackets inflated, so that swimming on the surface was no problem, despite the air tank and weights we were wearing. When ready to descend, we deflated our jackets.
We descended slowly and cautiously, in a line, holding on to the anchor rope. While descending, it's necessary to clear your internal air passages repeatedly, otherwise you suffer from pressure effects, as in an aircraft. In an aircraft, I clear my air passages by yawning, but it's difficult to yawn successfully underwater. The approved method is to hold your nose, keep your mouth closed, and blow. I had a little difficulty with this, and the Frenchman had more difficulty, but in such cases you just stay where you are (or go back up slightly) until you manage it. Eventually we arrived at the bottom in equilibrium with the pressure of the surrounding water.
After Suzanne had checked that we were all OK, we proceeded to swim about slowly, looking at the fish and the coral, keeping close together.
Although in a sense the experience was similar to snorkelling — we saw more or less the same fish and the same coral — nevertheless it was a superior and more special feeling to be down there like a true sea creature instead of just watching from the surface. Suzanne later complained that the underwater visibility was poor, and indeed we couldn't see clearly for long distances; but we could see everything around us reasonably clearly, watching the fish going about their everyday business. Again, they showed little or no fear of us, and sometimes came almost close enough to touch. These were mostly little fish, smaller than my hand, though there were some that may have been up to half a metre long. On the whole, the smaller fish were more colourful; the larger ones tended to come in murkier colours.
Later I bought a fish chart and was able to identify a few of the fish I'd seen: the blue-green bridled parrotfish, the red immaculate soldierfish, and the little black-and-white sergeant majors.
I had some trouble with my mouthpiece: it was feeding me more air than I wanted. At one stage I was quite disturbed by this and thought I'd have to go up; but it became more manageable after that. However, the effect was that I used up my air quicker than the others (I kept looking at my air gauge), so I had to go up early anyway.
Going up is easier than coming down, but you still have to go slowly, breathing steadily as you go, so that the compressed air inside you can gradually come out.
Back in the boat, someone told me that a five-foot whale shark had been sighted on the surface while we were down. I wondered if he was joking. Later I looked up the whale shark and discovered that it eats small fish and plankton, and is harmless to humans. However, it's the largest fish in the sea and can be up to fifty feet long; a five-foot shark may have been some other kind...
When the others came up, I mentioned my air problem to Suzanne, who was initially sceptical (she thought I'd just been breathing too fast); but she checked my equipment and confirmed that the diaphragm was leaking (the diaphragm normally prevents air from coming except when you breathe in).
Better too much air than not enough, I suppose.
You may be wondering what happens in the not-enough-air scenario: if your scuba somehow fails completely, or if you forget to check the air gauge for too long.
It may be possible to reach the surface successfully without air, depending on how deep you are; but it's tricky. You have to breathe out air in little bubbles all the time, to let the compressed air inside you come out. If you go up too fast, you get internal damage from the compressed air; if you go up too slowly, you drown.
Fortunately, there is a better solution: you share someone else's air. Some scubas are fitted with two mouthpieces so that this can be done easily (Suzanne always had a spare mouthpiece); otherwise, you and the other diver must share his mouthpiece like a peace pipe.
For this reason, and others, diving by yourself is not a good idea.
People are quite commonly nervous on their first dive. I had two moments of apprehension: one during the morning lecture, when at one point I began to feel that diving was more complicated and dangerous than I'd expected; and the other when I was ten metres down and realized that my air supply was misbehaving.
However, when I started my first dive I didn't feel particularly nervous. By then, I felt I understood what I had to do, and we'd already tried the equipment in the swimming pool. It seemed that I was in no significant danger as long as I went down slowly and came up slowly.
The only thing that worried me in theory was something that Suzanne told us about beforehand. Apparently it is possible for a diver to descend without problems, but to get a blockage in his air passages on the way back up. This is bad news, because you'll experience pain and perhaps internal damage if you come up with compressed air trapped in your sinuses (or wherever). I'd be interested to know what the chances are of suffering from this problem; very low, I hope.
A couple of days later I went for a second dive — that is, I repeated the afternoon session without bothering with the morning part. This second dive was more successful: my equipment worked properly and I stayed down much longer: for most of an hour, I think. I also felt more comfortable with the equipment and the fins. I even began to wish I'd hired an underwater camera from the Centre (someone else hired one; Suzanne borrowed it underwater to take a photo of him).
The maximum depth we reached was about 14 metres the first time and 13 metres the second time; though mostly we stayed around the 10-metre level, at a comfortable height above the coral. On the second dive, I realized that one of my gauges was a depth gauge, so I was able to check the depth myself.
It's obvious that water is heavier than air, but I hadn't really thought about it, and was rather surprised to read afterwards that the pressure at 10 metres down is already double the normal atmospheric pressure. Fortunately, the human body is mostly made of water, which is not compressible. The air tank contains compressed air, which brings the air inside the body up to the same pressure as the surrounding water.
Scuba diving book
My scuba diving book is Learn to scuba dive in a weekend, by Reg Vallintine, published in 1993 by Dorling Kindersley Limited, of London. It's a slim hardback, costing £8.99 in England, and seems to be an excellent introduction for beginners. Vallintine is evidently a recognized British authority on diving, and the book is beautifully produced, with copious colour photographs illustrating the text.
One oddity: the book persistently and jarringly uses a plural pronoun to refer to a single person who may be male or female. Example (from a section on training for emergencies): “Ideally, the victim should be positioned on their back, with their head clear of the water.” Judging from his photograph, Vallintine is old enough to know better than this; probably his editor was responsible.