To pass the PADI Open Water certification, you first work on the theory, reading a book (245 pages) and/or watching videos (4 hours 30). I read the book in 3 days, watched the videos in x2, and passed the quiz. Reading the book was not worth the time… What’s most important to remember is the risks and how to avoid them; here I review the ones I found most interesting, then give a summary of my first experience.
Risks
Air
- Squeezes: As you descend, squeezes occur when the air pressure inside a diver's body air space is less than the pressure of the surrounding water. This condition can cause discomfort, pain, or even injury. To equalise, gently pinch your nose and blow. While descending, this is done at every meter.
Air is composed, roughly, of 21% of oxygen and 79% of nitrogen — ignoring the other dozen gasses that make up less than 1% of it. The default cylinder countains air with these proportions but with high pressure.
The most important rule of diving is: Never hold your breath to avoid lung overexpansion. Besides this ascending rule, four issues relate to air components:
- Oxygen toxicity: Oxygen is toxic under high pressure. The limit for normal air is 40 meters, way deeper than the 18m covered by the Open Water training. When breathing 100% oxygen air, the maximum depth become 6 meters — and it requires special training.
- Contaminated air: impurities that are harmless at normal pressure may become harmless down in the water.
- Decompression sickness: The deeper you are, the faster air nitrogen dissolves in your tissues. The longer you stay in water, the more time you give nitrogen to go your tissues. If the excess nitrogen is not properly expelled through blood circulation and the lungs, it may result in bubbles forming in your body. An online computational decompression model of this phenomenon helps planning a dive that prevents it. Ascend slower than 18m/min and have the three-minutes safety stop at 5m.
- Gas narcosis: Narcosis (drunk-like effect) can be caused by the anesthetic effect of certain gases at high pressure. Diving, it typically does not occurs before 30 meters deep.
Water
Water conducts heat from our body 20x faster than air. Hypothermia thus is a risk, and most dives stop because a diver feels cold. I was feeling cold only after the dive, when allowing my body to cool down. That’s probably because I was moving too much underwater (see below).
Lost
This is obvious in theory but happens surpinsingly quickly. You focus on something for a few seconds (oh, a fish!) and no longer see your diving buddy(ies). Search for one minute then ascend and find them at the surface. At one point I lost my instructor, turned around for 20 seconds, and saw him coming to me.
Experience — Don’t run
Had my first experience of scuba diving today. It was extraordinary. The first underwater breath is something else: you literally enter another world. You enter a real life video-game, with the instructor that gives you hand signals to make you move, and the screen defined by the sides of your mask. Up, down, straight, breath, equalise, go deeper pulling on the mooring line. He moves and you follow. He does an exercise then signals you to do the same.
The most important skill to develop is that of buoyancy (floatation, the goal is to be neutral) and trim (balance of floatation so that you are naturally horizontal). For me, it was not a matter of doing well, but a matter of seeing well: being blind as a bat, I need to be amazingly close to what I’m looking. Hence, within 3 minutes of floating around I had developed a satisfying breathing and BCD (Buoyancy Control Device) control to hover centimeters above the bottom and glare at the coral without damaging it.
I expected to panic more, but this didn’t happen at all. In fact, removing the breathing device (secondary stage of the regulator) from my mouth was very liberating. From an exercise to do once, it quickly became my normal practice, swimming mouth-free for a few seconds as I danced among the fishes. Another girl was had started the day before told me on the boat that this made her panic, so this experience may not be universal. It reminded me of the story that, as a baby, I enjoyed my first swim in a pool so much that I was just thrilled to be underwater and didn’t try to breath. It seems to be the same thing I experience now when removing the regulator. Ask your parents how was your first swim and you may predict how is your first dive.
The downside was clear though: with all these unnecessary movements (chasing fishes, strong accelerations and decelerations, removing regulator, admiring ascending bubbles, chasing said bubbles, attacking bubbles, win over the bubbles, becoming a bubble God — giving life and death to big bubbles), I was using my air more than twice as fast my instructor, reducing drastically the dive time. It’s just like the Colombian salsa teacher told me last week: Don’t run. It’s not a dancing nor a diving advice but a lifestyle advice, which has now become a goal of this trip.
Next dive, I plan to use less air than the instructor. Next dance, to go slower than the teacher; unless the music begs to differ.
