24 April 2010

Don Quico

Today (Friday), I did a big dive. The biggest, by far, I've ever done. It was to a purpose-sunk wreck of a tug boat called Don Quico. Don Quico rests in a sandy area in about 60 meters (200 ft) of water. Because it's so deep it's protected from most surface weather and remains intact.

Game Face

All week we had been building the skills I would need for this dive. Each dive was progressively more advanced and the training drills more challenging. Denis (my instructor) had me practicing things like dropping and recovering my tanks, removing and replacing my BCD, deploying a surface marker buoy, responding to "failed" equipment, transferring tanks between each other, and (the craziest of all) a swimming out-of-air simulation without a mask while at 130 feet of depth! Today, however, there were no drills. This was game day.

The objective was to spend 20 minutes at 50 meters on Don Quico. That probably sounds rather straight forward, but that amount of time at that depth requires nearly an hour of decompression! To do it, we needed to carry four tanks each - two 80 cubic foot tanks on our backs (filled with air), another 80 cubic foot tank on the left side (filled with 32% Nitrox), and a 40 cubic foot decompression tank on the right side (filled with 78% Oxygen). The reason for so many is threefold - breathing gas is consumed very quickly at extreme depths due to high ambient pressure, oxygen rich mixtures help to accelerate decompression, and low oxygen mixtures to avoid toxicity.

Denis' wife Carmen

Carmen was just cleared by her maternity doctor to start diving again, so she came along with us. The doctor told her it was okay to dive, but to "just take it easy at first." She joked that she was taking it easy - she was going to 50 meters instead of 100 on her first dive back! Like Denis, she's also a very experienced diver.

Learning from the Jedi Master

I wouldn't dare bring my camera along for a dive like this the first time, but I asked Carmen to take a few pictures while we were down there. The underwater housing for it, however, is only rated to 40 meters, so we had to leave it at the mooring line while we went to the bottom (sorry, no pictures of the wreck!).

The site is absolutely perfect for a new technical diver. The mooring is at 20 meters in a reef. Adjacent to it is a sandy slope that goes directly towards the wreck. This feature helps with orientation and even better to allows you an ascent with things to look at (otherwise you'd be surrounded by blue with nothing to do). At the base, Don Quico rests in a sandy plain, and beyond it is the "wall" - essentially a vertical underwater cliff, starting at 60m and going well beyond the current attainable depths for divers.

At 30 meters on the descent, we switched off of our "stage" bottles (just before the 32% Nitrox in them would become toxic) and onto compressed air. Air allows us to continue deeper as it remains safe to breath until between about 56 to 66m. The higher nitrogen content in the air, however, causes increased narcosis (i.e. peripheral narrowing, slowed reaction time, distorted perception of reality, reduced dexterity, etc). I'm pretty well practiced at keeping nitrogen narcosis under control at a depth of 40m (my limit until this course), but this is the first time I was going to push significantly beyond it.

When we arrived at the deck of Don Quico, we detached our stage and decompression bottles and left them behind. There was no need to carry them around the wreck. We were now at a depth of 51 meters and my vision started closing in - the narcosis was intense. It's the first time I've really felt it effect me like that. I was expecting it, though, and was prepared to handle it. It's not possible to build a tolerance to nitrogen, but you can train yourself to overcome the more debilitating effects of it.

We started to make our tour around the wreck, and I focused on seeing the things being blacked out by the narcosis and on making coordinated movements. I was able to push it back enough to feel in control of the dive. It made me think about the guys from Shadow Divers who were breathing air at 70m in the beginning (well beyond the toxicity limit). That's beyond incredible. We circled the wreck twice and then went off the bow to the wall and hovered above it. Looking down, I thought about the next step, a Trimix course - which would allow me to go off the wall and double the depth I was currently at, reaching the limit of what is currently possible for divers. That's like climbing Mount Everest, except down.


I reached a maximum depth of 55 meters (181 feet). We returned to Don Quico, picked up our tanks, and began our ascent. My first decompression stop was at 32 meters. At that point my computer told me I had 54 minutes to go (54 minutes of decompression!). If I arrived on the surface anytime before that, it was bad-news-bears. When we returned to the mooring line, we retrieved my camera and got a few photos on the way up. There was a big school of Bar Jacks hanging around the mooring line and a couple of big Cero Mackerels that passed by, but my attention was focused too much on the decompression to really take that in. It'll be sometime before I'm at ease 100% on a dive like this. We got back to the surface without incident. Mission accomplished.

Carmen, Denis, and our boat driver, Tito.

The Golden Arrow Dive Center dog, Lola.

I hope these posts about technical diving haven't been boring and too, well, "technical."

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