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Compressed air and open water

I got my basic PADI Open Water certification in Thailand in the summer of 1999. Since then, I never took another breath of compressed air until the Saturday before last, and I didn’t go diving in the open ocean until yesterday.

Yesterday, I boarded a boat with about 20 other divers at the Fremantle docks and we cruised over to Rottnest Island. The trip took about 40 minutes. I spent most of that time talking with a Japanese guy named Kensuke. I lived in Japan twice for a year each time in the early nineties, so we had a lot to talk about. I was glad for the conversation, because the seas were a bit rough, and without a mental focus I tend to get seasick. I think he was glad for the conversation because, like just about any non-native English speaker who studies English in their own country, Kensuke studied American English and he had difficulty following Australian English, so few other conversations stood open to him on that boat.

I’ve spent many an hour conversing in English with Japanese people whose English skills ranged all over the spectrum of proficiency, so I’ve got a pretty good grasp of how to speak to them in a way that avoids confusion. I’ve developed a different mode of speech for making myself understood by Australians. I was rather surprised when we first arrived in Australia that people had trouble understanding me and remarked about my accent. My accent? I don’t have an accent. Oh, wait. I guess I do.

Anyway, we got out to the first dive site, and I got “kitted up” as the Aussies say, made my way to the back of the boat and took my giant stride into the dark choppy water. Grey clouds obscured the sun, and from the boat, the water’s surface stood as an impenetrable barrier to my vision. I feared that I wouldn’t see much at 18 meters depth because of the gloom. Once I got there, that fear proved unfounded. Getting down there proved more difficult than I had expected.

On the boat, I put 21 kilos of lead weight on my belt. In the pool the previous week, 21 kilos overcame the buoyancy of my body and of the wet suit and allowed me to decend at will. Salt water increases a diver’s buoyancy, and one of the dive instructors weighed me down more by slipping another weight into my BCD (buoyancy control device; basically an inflatable vest). I had hoped to avoid this because weight in just one side pocket leaves me unbalanced, but since it’s such a bitch to get out of the water, I offered no argument.

Even with the additional weight, I never sunk more than a meter below the surface. A female dive instructor signaled me back to the surface, and once there, she told me to relax and breath out as completely as I could, to get the air out of my lungs. Time for a little underwater yoga. (I started to write a journal entry last week after my day of training at the aquatic recreation center. In that entry I talked about the similarities between yoga and diving, both of which require cultivating an increased awareness and control of the breath. The thing got entirely too long and technical, and I have yet to return to it to pair it down.) I triggered my intentional relaxation response, exhaled smoothly and completely, and sank.

This first dive took place at a site called ‘the Colander’. I sank, feet first, to what I took to be the bottom. I pumped some air from my tank into my BCD and waited there for the divers to congregate around the various instructors. As I waited, squeezing my nose while trying to force air through it to compensate for the increased water pressure, I noticed that I had not reached the meeting place. It lay another 8-10 meters down. I learned this when I saw other divers disappearing into a large hole in the ocean floor. Lee, my dive buddy, a DIT (dive instructor in training), the low man on the totem pole and the recipient of a lot good natured ribbing from the senior staff, motioned for me to follow him and then disappeared into the Colander.

I proceeded head-first over the lip of the opening and descended to the real bottom, equalizing when sudden pain in my ears reminded me to do so. The false bottom, consisting of rock and sea grasses, drank up the light. The real bottom reflected light off of its white sandy bottom that seemed brighter than the diffuse light from the surface. Kicking to overcome my slight positive buoyancy, I pushed my way down into its glow as rocky walls enclosed me on four sides.

The other divers in my group were doing a dive required to receive their open water certification, so they had to perform a number of skill drills that we had done together the previous week in the pool. I already had my certification, so the senior instructor had me do some fin pivots to demonstrate that I had reasonable control of my buoyancy and then motioned to Lee that he and I should strike off on our own.

I expected Lee to swim up and out of the hole to begin our pleasure dive. Instead, he disappeared into a crevice in the wall. I swam to the wall, and dubiously examined the opening into which he had disappeared. Had I not seem a scuba-encumbered human go into that crevice a few seconds before, it would not have occurred to me that it might accommodate a diver. For a moment, I thought about looking swimming up to the false bottom and looking for a more open route, but then I followed Lee into the crevice as he and I both knew I would. While Lee glided through tiny tunnels of rock without ever making contact with the sides, I bumped my tank on the ceiling, brushed outcroppings with my fins, and steadied myself with by placing a hand on the rock wall on two occasions. A diver can kill living coral with a slight touch of skin or brush from a plastic fin, which makes buoyancy control so crucial. I hope I didn’t do any damage, but I wouldn’t swear under oath that I left that patch of ocean just as I found it.

Before yesterday, I thought that cave diving required a level of certification above my basic Open Water Diver level. I guess not. For most of that first dive, a rock ceiling stood between me and the surface, but I took comfort in the knowledge that the most dangerous thing I could do at that depth would be to panic and bolt for the surface with a lungful of compressed air. If I got in trouble in an overhead environment, bolting for the surface would not be an option, and I would have to keep thinking. Outside of our native environment, panic and a reversion to instinctive behavior kills.

As I returned to the surface, I saw that numerous streams of bubbles issued from the rocks of the false bottom. When I see large colorful salt water fish underwater, I find it hard not to imagine myself inside a giant aquarium, the streams of bubbles making their way to the surface suggested hoses snaking under the aquarium floor leading to buried air stones.

As I mentioned earlier, climbing the ladder back onto the boat while laden with a large metal tank and a weight belt takes quite a bit of effort and concentration.
After that first dive, the crew broke out a gas grill and prepared a fine lunch of chicken sausages and fresh crayfish tail. When I say fresh, I mean fresh. Those crayfish started the day on ocean floor and came to surface more recently than I had. Yum!

As I awaited my turn take my second giant stride into the Indian Ocean, the guy in front of me sang a verse from "Sweet Home Alabama."

"Great," I said, "now I’m going to have a Leonard Skynard song running through my head while I’m underwater." Then I realized that during my first dive, I didn’t have much of anything running through my mind. Usually, if I’m not humming or whistling a song by They Might Be Giants, the theme to a children’s television program (say, Thomas the Tank Engine), or a cell phone ring, I’m composing some narrative or essay or rehearsing some imaginary dialog. The demands placed upon my concentration by the process of diving along with the novelty of the underwater environment took up the bulk of my attention and left little cognitive RAM free to be occupied with the usual mental gibberish. As I get more comfortable with diving and shift more of the cognitive tasks it imposed on me to autopilot, I imagine that the mental fidgeting will return, so I decided to savor the lack of brain chatter on my next dive. Of course, once I got down there again, I forgot to do so.

The second dive went much like the first, though we spent our time swimming through winding underwater canyons with less time in actual caves. The underwater landscape, consisting largely of plants that swayed in the current, seemed to sway and pulsate, and took on a rather psychedelic cast at times. For a while, I sat on the bottom watching the bubbles from my exhalations trail to the surface. According to my dive computer, I reached a maximum depth of 17.9 meters on that dive. It may not sound like much but it would make for a long fall and a longer struggle to the surface if something went wrong with the flow from the tank of compressed air on my back.

The combination of the big lunch and a bit of sea water that went up my nose and down my esophagus had me wondering what I should do if I suddenly needed to puke at that depth. I really had no idea. I didn’t imagine that I would manage to keep myself from inhaling at the end of a retch before I got my regulator back in my mouth. I thought that I should start my ascent early rather than face that possibility, but I resisted. I knew that I would probably not make another dive any time soon, and I wanted to get the most out of the present opportunity. Looking back on it now, that thought seems ludicrous to me. Lived wisely, my life will stretch for decades if not centuries. To risk it for just a few more minutes in that environment smacks of cost/benefit calculus and risk analysis gone thoroughly to seed.

When I did decide that I could no longer ignore the signals from my stomach and started my ascent, I looked at my pressure gauge and saw that I had just 40 bar of air left in my tank. I started each dive with 200 bar in the tank, and the diving instructors told us to ascend with no less than 50 bar remaining.

In total, I spent 63 minutes underwater yesterday, and to do so, I had to change tanks between dives. The previous week, I spent over two hours underwater on a single tank, but the pool had a maximum depth of 3.8 meters, and the deeper you dive, the quicker you use up your compressed air.

On the trip back from Rottnest to Freo, someone spotted some dolphins, and the driver slowed the boat so we could get a good look at them. They broke the surface several times, getting closer to the boat each time. The last two times they broke the surface I could see clearly that one of the dolphins dwarfed the other. It was a mama and her baby.

All in all, it was a very good day.


( 5 comments — Leave a comment )
May. 5th, 2003 09:22 am (UTC)
(I started to write a journal entry last week after my day of training at the aquatic recreation center. In that entry I talked about the similarities between yoga and diving, both of which require cultivating an increased awareness and control of the breath. The thing got entirely too long and technical, and I have yet to return to it to pair it down.)

i'd like to read that.
May. 5th, 2003 05:23 pm (UTC)
Such as it is
Here's as much as I wrote before abondoning that aborted entry:

Underwater Yoga

I spent Saturday taking a scuba refresher course in an enormous indoor aquatic recreation center. I originally got my PADI open water certification in Thailand in 1999, and I hadn’t taken a breath of compressed air since then. When I took my original training, I spent half a day in a “classroom” watching videos and taking very simple quizzes, and then I spent about half an hour in a pool with the instructor practicing removing and replacing my mask and recovering my regulator. The rest of the basic skills we covered in a rapid checklist fashion the next day in open water.

I didn’t realize what cursory training I received in Thailand until taking this refresher course here in Australia. We spent 9 hours at the aquatic center, and a good deal of that time we spent under water. Rather than running thru the basic skills in a “get it over with” fashion, we moved thru them methodically; repeating them several times until I grew fairly comfortable with each exercise.

Soon after Lara, Logan, and I set up house here in Fremantle, we joined a nearby fitness center where I’ve been studying yoga. Every yoga class starts with directing attention to the breathe, learning to fill and empty the lungs with a consciousness and completeness that I rarely find reason to practice outside of yoga class. Much of the underwater work I did on Saturday seemed to be aimed at cultivating a similar consciousness of and control over my breathing, learning to breath in a certain way, and doing it consciously when my hard wired reflexes urged me to do something else.

Part of the basic scuba
May. 5th, 2003 06:33 pm (UTC)
Such as it is Part 2
Part of the basic scuba kit is an inflatable vest called a BCD (buoyancy control device). While diving, one desires to maintain neutral buoyancy; neither sinking nor rising. Wet suits provide buoyancy which we counterbalance with lead weights worn on a belt. These two items roughly negate one another, but once underwater, maintaining neutral buoyancy generally requires some additional tweaking. One way to do that is to pump some compressed air from the tank on your back into the BCD to provide additional buoyancy and then releasing air from the BCD when you notice that you’re rising without meaning to. The BCD, while useful for floating effortlessly at the surface, works as a pretty blunt instrument for buoyancy adjustment underwater. The lungs work much better for this purpose because the brain receives direct information from the lungs about the volume of air they contain and can issue instructions to make rapid and minute corrections. For example, if you’re swimming near the bottom and you notice you’re about to make contact with something like a coral formation that you shouldn’t touch, you can fill your lungs for a quick lift.

If one fills one’s lungs at the surface, dives and then comes back up, the air in the lungs will compress the deeper one goes and then expand again on ascent, but it will never expand beyond the original volume. The greatest danger in diving involves taking a lungful of compressed air while underwater and then ascending rapidly while holding that breath. As the diver approaches the surface, the air in the lungs expands. If the airways are open, as they are while exhaling, then the expanding air will be forced out without harm to the lungs, but if the diver holds that breath, keeping the lungs closed, then that expanding air will have no escape route and will burst the lungs.

When depending on air carried from the surface in the lungs, holding the breath is a good idea, and our reflexes serve us well. The natural inclination to conserve the oxygen in the lungs stops working and becomes a liability when we introduce compressed air into the equation. So long as the diver acts according to his understanding of depth and compression, it’s all good. Unfortunately, when panic takes over, we revert to our natural inclination, which, outside of the environment which shaped it, leads to disaster.
May. 6th, 2003 05:00 am (UTC)
Re: Such as it is
doh! feels like i was watching a movie that suddenly went black.

but that's cool. that's a neat concept comparing scuba diving to yoga. i'm a blue belt in kung fu and my instructor told me that when i get to green belt, he'll let me start with tai chi training. i can't wait for that. he also told me there's more to yoga than what is usually taught. he said there's a form of "extreme yoga" that's really the original, or closer to, than what is being taught in most places these days. he didn't go into detail, but i gathered that it was more of the really crazy postures that you see old yogis doing. (that remind me of dhalsim off of street fighter. heh.) do you take this form of yoga, or the other?
May. 6th, 2003 06:41 am (UTC)
Re: Such as it is
There's more, it just woun't all fit into one LJ reply. If you go back to the journal entry, I put the rest in second reply.

I take yoga at my fitness center. It's taught for a general audience and doesn't venture far beyond the basic postures which I suspect are common to most forms of yoga.

I studied Tai Chi Chuan in the US. That's something I'd very much like to get back to.
( 5 comments — Leave a comment )

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