So, I realize that the collecting trip looks like it's all fun and leisure ... and it is for the most part; our work is fun work, but with a VERY healthy dose of safety. Today's dives really highlighted the precautions we take when diving. Up until today our dives had been no deeper than 45 ft., but today we found a new dive site. When we swam down and hit bottom our gauges read 77 ft. We were all looking at each other with that "whoa" look on our faces (which looks really different through a dive mask.)
But why does going deeper require more caution? There's something about nitrogen I don't quite understand, but I just spent an hour talking with Captain Lou (a VERY experienced Dive Master) to try and understand why we stop and hang out in one spot for a few minutes on our way to the surface.
Here's my layman's attempt to explain it. The deeper you go, the more pressure is put on your body. Oxygen still moves through your body as you inhale and exhale, but for some reason, nitrogen tends to build up and not flow through your body the way it should. Coming to the surface slowly (a gradual release of pressure on your body) allows your body to gradually reabsorb and release the built up nitrogen.
The deeper you go, the more it builds up, and the more time you should give you body to readjust. If that doesn't make any sense, please do not hold it against Captain Lou, he tried his best to help be understand. On a side note ... We also bring the fish we've collected to the surface very slowly by leaving them in a barrel underwater and slowly raising it onto the boat. Fish have a swim bladder, an air filled sac, that controls their buoyancy in the water. If we bring them to the surface too fast, the air in their swim bladder can expand, causing them to float and tilt to one side. Not good.
Okay back to safety. I do know this about deeper dives ... it's darker, and you're further from the boat which makes it harder to orient yourself and make sure you haven't strayed too far. When diving at any depth there may also be currents that can cause you to slowly drift away. As a precaution we always dive with a buddy, and we always take a compass reading so you know which direction to swim to get back to the boat.