18 August 2009

Deep Diver

Yesterday, I completed my "Deep Diver" specialty course. I can now dive to the recreational limit of 132 feet. The course required a knowledge review and three instructor-supervised dives to 132 feet. There are a lot of special considerations when diving to a depth like that. First is the pressure. At that depth, ambient pressure is 5 times the surface pressure. Your body is mostly unaffected by this because it's almost entirely water, but if you don't equalize pressure in air spaces (ears, sinuses, mask) there can be problems. That's not really any different than shallower diving, you just have to do it more as you descend deeper.

Second, as a result of increased pressure, your air consumption is much greater. The air you breathe is also 5 times as dense, so you use it 5 times as quickly than you would at the surface. For somebody like me, who has big lungs, you need to monitor your air supply carefully. Third, because the air you breathe is do dense, your body absorbs nitrogen far more quickly. You have to "offgas" that nitrogen before returning to a lower pressure environment or you risk forming nitrogen bubbles in your bloodstream - known as "the bends." As a result, the amount of time you can spend at depth is limited. The time you can spend down there is known as your "no decompression time," the amount of time you have at a certain depth without needing to make a mandatory decompression stop on your ascent. Today, no decompression time is calculated using a dive computer that you carry with you.

Finally, you have to be aware of nitrogen narcosis. When your body becomes saturated with nitrogen it can have disorienting effects. The nitrogen interferes with your body's processes, causing delayed response time, overconfidence, mild tunnel vision, and idea fixation. Really, I just felt a little tingling sensation. It's completely harmless, and the effects disappear when you ascend even a little bit. It can happen to some people as shallow as 100 feet, but I didn't feel anything above 125.

Technical aspects aside, there's a whole different world just a little bit deeper. Some of the more interesting corals and sponges only grow at greater depths. Certain species of fish and crustaceans only live in deep water. There were a couple ledges with a type of algae that looked a lot like terrestrial vegetation and a type of sponge that looked like giant fungus that would grow out of a decaying tree. It could have been a landscape that you'd see in the Olympic rainforests of Washington, if it hadn't been nearly 40 meters underwater.

For me, though, deep diving isn't something I'll probably spend much time doing. I'm glad I'm able to, but that amount of time you can spend down there is so little (due to increased air consumption and no-decompression limits) that it's just not worth it. I'm content diving to shallower depths, where you can stay longer with fewer complications.

No comments:

Post a Comment