Oh yes you do! On every dive! It says so right in the law book. Laws of physics, that is.
As sport divers cruising the coral reef or seeking out the best site for underwater photography, we tend to lose sight of the fact that we are on-gassing —or absorbing nitrogen into our tissues—as we dive. As we think back to our SDI Open Water Diver course, we recall that during our descent, our bodies absorb nitrogen from the air we breathe, thanks to our dive buddy, Henry’s Law. We also recall that the longer we stay, or the deeper we go, the more nitrogen we absorb. Every new diver learns this. and also learns not to exceed the limits detailed by their dive computer. So, while we are at depth exploring that shipwreck, observing marine life, or searching for that lost object, we continue to absorb nitrogen.
“Ah… but I don’t perform decompression like my technical diving friends do,” you may say. “I can return to the surface anytime I want,” you add. Well, true. Maybe. Kind of.
The fact is that even as sport divers, even when following the directions of our dive computers, we still have to off-gas—or release the nitrogen from our tissues—as we return to the surface. While we are not planning any decompression stops, other than a safety stop (more about that in a moment), our dive buddy Henry from Henry’s Law is still having an influence on us. That influence is called decompression.
As we ascend, again following all the rules and common sense things we learned from our scuba course, nitrogen is being released from our tissues in a nice, slow and controlled manner. Just the way we like it. We’re decompressing. Actually, sort of like a deco dive. There, I said it! A deco dive. And we’re sport divers! Simply said, sports divers are not immune from the laws of physics and the gas laws. So in reality, every dive is a decompression dive. It is not unusual for sport divers to make repetitive dives in a day. Often times, surface interval time can be spent on the surface snorkeling without our dive buddy Henry impacting our bodies. Remember, we’re at 1 atmosphere/bar at the surface, so we can take full advantage and still view the sights as we’re off-gasing.
However, we do like to make a stop. A safety stop. We all know that a safety stop performed at the end of our dive at about 3 meters/10 feet is just a good common sense thing to do and it only takes a few moments, perhaps 3 to 5 minutes at most. It allows our bodies to adjust, allows a little more off-gassing to occur prior to getting out of the water. I’ve found that this delay in my ascent is the perfect time to reflect on the dive I’ve just made and to briefly think about my exit from the water. And frankly, you never know what you’re going to see at that depth. I recall one shore dive in a fresh water lake in Maine performing a safety stop at the end of the dive. It was near a long forgotten coal dock where I spotted an old prop from a passenger steamer that plied the waters of that lake in the late 1890’s. I spent the remaining few moments of that safety stop planning my next search and recovery dive!
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