Obligation. One of those words that, through trite usage, has lost its intended impact. Common appearance of the word in legal context is partially responsible for this dulling of what is historically a monumental concept. To be obliged to someone or something, bound by morality, by honor, by a sense of duty, commitment, or plain necessity; that’s serious. Recently I have been contemplating the gravity of the word in the context of decompression obligation.
The pressure exerted by the weight of water pushes nitrogen from inspired air into solution in the bloodstream, more nitrogen than the body would normally have at sea level. Increase in the depth and time spent underwater loads more nitrogen into the body’s tissues. Eventually the diver must return to the surface, preferably slowly, so that as the pressure lessens, excess nitrogen has a chance to come out of solution, return to its gaseous state, and be harmlessly transferred to the lungs and respired. Rapid depressurization during quick ascent causes the nitrogen to, instead of leaving through the lungs, form bubbles in the bloodstream. If those bubbles collect and join together, then move into vital pinch points such as joints, heart, and nervous system; bad things happen. Think of opening a soda bottle after you shake it up. Open the lid (ascend) slowly and the bubbles hiss away harmlessly. Rip the cap off in a single motion and the pressurized gas in the bottle comes out of solution and fizzes out all over the place, not dissimilar to what can happen in the body.
Extended time spent at depth causes enough nitrogen accumulation, or loading, in the body that the diver cannot proceed directly to the surface, but must make a series of planned stops on the way up to allow the nitrogen a chance to slowly and harmlessly come out of solution. These stops are called decompression stops. Basically, it means you twiddle your thumbs in shallow water holding on to a bar affixed to the boat or you hover or play paper rock scissors with your buddy or count jellyfish or watch the minutes tick by on your watch, as long as you don’t come to the surface until your decompression stops are completed.
Required decompression stops are also known as decompression obligation. The diver is obliged by nothing less than the laws of physics, gasses, and biomechanics to not proceed directly to the surface. Obligation. Serious stuff.
It’s not just that the wrecks here are deep. It’s that they’re deep and, for the most part, horizontal. So, unlike reef diving, where a dive plan might be to go deep, look at something, and then spend the rest of the dive slowly ascending while cruising the reef, eventually ending up in shallow water, the dive plan in Truk often involves going deep, staying deep, then coming up. This practice leads to decompression diving and also a different perception of depth than I have before experienced.
I rarely get in the water now without hitting 100’. Once you get used to descending into the engine room of a ship at 130’ and staying there up to or beyond the point of creating a decompression obligation, exiting the structure or moving up a few levels in the wreck to, say, 80’ starts to seem like a relief. I haven’t in my diving history found myself saying, “Thank goodness I am only at 80’ now. I’m home free.” 80’ seems reasonable, 60’ is downright shallow, just a depth through which I pass to get back to the boat, and at 40’ I’ve started to depend on my body to begin efficient offgassing. The depths which I used to consider deep are now shallower stops along the way up from depths at which I have spent considerable time.
Lest you think me glib or careless, let me assure you that the seriousness with which I consider this issue is what brought me to reevaluate the term obligation as it relates to decompression. Ignoring an obligation underwater can have the same dire consequences as blowing off a moral, legal, or personal obligation, but in a much more immediate arena. Sure, you may sometimes be able to cheat the laws of theoretical physics in the same way that you can try to sidestep a financial or legal obligation, but if you fail or you get caught, you can be in serious trouble. Moral obligations may be overlooked, but the guilty aftermath experienced by an essentially moral person are not unlike those experienced by a prudent diver overlooking decompression obligation. To be obliged to do something is a heavy responsibility.
