No Boom!

Do you remember where you were when you first learned that you wouldn’t explode if you overstayed No Deco Limits?


Did you read it in some diving pseudo-thriller? Were you on a boat surrounded by people in a ton of gear? Did you accidentally actually overstay and trust your computer to the surface? Did it come as a revelation?


I was first introduced to the idea on night two or three of my Open Water class. In this dried-wetsuit smelling classroom in Alexandria, VA the instructor casually mentioned that he had friends who would stay far past NDLs, breathing all sorts of weird gasses, and then have to hang on a dark anchor line for ages, somehow getting rid of nitrogen. He mentioned it all dismissively, as this were the sort of thing that only a dangerous sociopath would do.


He was the instructor, and he knew everything. So, naturally, I went along for the logistical ride, agreeing that NDLs were hard, fast, and inviolate lest I wanted to tempt fate.


For a fleeting moment, however, the image of the USS Monitor popped into my head. My Dad is a civil war buff and I knew the history of the ironclad well, including that it had been found quite deep. I wondered if these odd daredevils were the sorts of people who would dive there; what it would be like. And I wondered if I’d ever be one of them.


So that was the very first time I’d heard tell that deco diving was a thing. But for some years afterwards I, like so many divers around the world, thought of NDLs as a sort of floor, below which there were only sea monsters and a painful death from the bends.


Over the years I’ve heard the topic treated this way consistently. With kid-gloves or in whispers. At quarries. On tropical islands. On liveaboards.


On a day-boat that made the long and somewhat arduous crossing from Kauai to private island of Ni’ihau the crew actually checked our computers as we climbed back aboard. If you had gone one foot deeper than 130’ you were done diving for the day.


I’ve watched an experienced advanced instructor freak out underwater because Nelly’s computer went into 5 minutes of deco.


The truth is that a lack of understanding about decompression diving is a bit startling once you have gained the exposure and knowledge around it. Especially among dive professionals.


Without inviting a gleeful round of agency-bashing, divemaster and instructor training spends a LOT of time and energy around sales. Gear or continuing education or trips... “Sell something!” is the doctrine.


I would argue (am, in fact, currently arguing) that perhaps some of that energy could be redirected into a more comprehensive understanding of decompression physics and physiology.


There are exam questions on the weight of seawater: who bloody cares? If I need to lift an object I’m going to inflate a lift bag until it’s neutral and then move it around... I’m not gonna do math. But if I, as a new recreational instructor, have a diver that has violated NDLs by 5 minutes... an actual and immediate safety practicality, and one that is certainly not unheard of:


Lacking any deco training myself, do I abandon them to avoid the dreaded bends myself? Ride our computers to the surface without any understanding of why the computer is doing what it’s doing? Cut them off diving for the day? Call DAN and eat up their time? Put the diver on oxygen and try not to lose my shit?


Or, worse yet, after this happens a few times (because, make no mistake, in vacation dive destinations this WILL happen) do I grow callous about it? Do I start bragging over evening beers, “PFT... NDLs. I dive like this all the time and I’ve never been bent.” Other than making you think you look like a bad-ass in front of vacation divers, what sort of example does this set?


Now you’ve got divers - even dive pros - who have been trained that NDLs are completely unbreakable... unless you are a mystical dive wizard or some sort of weirdo covered in lots and lots of black kit.


Despite the t-shirts and the stickers: it isn’t voodoo. It isn’t the dark side of the force. It’s physics and physiology. And it’s tested and proven.


According to the current model, and without restructuring the recreational instructor curricula, the only proper way in is some form of Deco training. Most every agency offers it in some version or another. Take the course, it’ll take a week or so. Hell, you’ve come this far — in for a penny, in for a pound.


Harsh as it may sound, I honestly feel like it should be, if not mandatory for dive professionals, strongly recommended and universally encouraged by the community.


Not in a ball-swinging, “I’m a bad motherfucker because I know how to do deco dives” kind of way. Even if you never, ever plan to deco dive in your life... simply for the knowledge of what is going on in your body and the bodies of those people your job is to protect.

What’s going on, in fact, during every single dive. Even if you never go past NDLs.


I would actually go one further and wish that any experienced diver (not just pros) should aspire to decompression training. Again, even if you never actually plan on doing anything other than 60’ reef bimbles. Because as an experienced diver, sooner or later, you’re going to wind up a little deep, or wind up staying a little long, or have a buddy that has done so.


You may, in fact, one day wind up with an insta-buddy that is a goddamn idiot and has ignorantly swum themselves down to 150. With the right training, you would be equipped to make the decisions required for an informed, capable rescue attempt then and there. Instead of having to wing it and hope for the best without any idea of what you might be getting yourself into.


Over the years since I first heard of it decompression diving has become far more mainstream and accessible. It’s not exactly back-room whispers, though there is still a great deal of misunderstanding and miscommunication around it.


The topic of quality of deco training is, perhaps best left to another time. But any exposure at all is going to be way better than the far-too common and pervasive misconception that you’re just going to get bent and die. Or that if you can just be awesome enough then you’re immune to inert gas saturation.


Or you may learn that you do, in fact, really enjoy deco diving. And you might get the opportunity to dive the USS Monitor. Like I did a decade after that image first had flashed, briefly, through my mind in that classroom in Virginia only to be just as quickly dismissed.


And if you get a chance like that: take it. It’s a hell of a moving experience.


Not gonna lie, though. 90 minutes of blue-water deco is boring as shit. Better in a cave where you can stage a book for the long stops.

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