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Graduation Dive February 2, 2009

Posted by Chris Sullivan in Dive Log, Technical Diving, Training.
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On Monday, September 3rd I got up early to get ready for the final dive of the weekend. A guy from the local dive shop brought a computer down to the motel so we could plan the day’s dive, 25 minutes at 165 feet. I worked out 20, 25, and 30 minute schedules using air as the back gas and EAN 50 deco gas, and wrote them out on white duct tape for both my wrist slate and one of my fins. The residue remained on my fins until I chucked them a few weeks ago because they were starting to fall apart.

Writing out deco tables on duct tape with a magic marker wasn’t easy, partly because I was writing them on a small space and partly because I kept making mistakes. I finally got a good set and then went on to check CNS and OTU, which were fine, with CNS about 23% and OTU well within limits. Finally we looked at our estimated gas consumption which was fine for this dive. Our tanks were filled to 3000PSI, a little bit over  the rated capacity but giving us 215 cubic feet to work with (the Fabers reputedly will tolerate 4500PSI without problems, as long as the burst valve is replaced – use this info at your own risk though).

Our dive started at Sparrow Island on the Lillie Parsons, where I’d dived 2 days before. This time, like the last, we’d gone to the Daryaw first, but we just waited on the boat while the others dived as we were only prepared that day to do the one dive. We were the first ones into the water when we got to the Lillie because we didn’t need a surface interval though.

I set up my dive computer for 21% O2 on Mix 1, and 52% O2 on Mix 2. I was carrying two deco bottles, and we were supposed to do a gas switches at 70′ and 30′, even though they were the same gas, to simulate using 2 mixes. Even though the computer was set up properly the idea was to use the tables as this was a training dive and I had my Tag-Heuer dive watch bought duty-free in Jamaica in 1991 as a backup.

We made our way to the Lillie Parsons in the usual way, descending down the slope against the current and away from the island then dropping down the wall. We made our way over the upturned hull, then straight down to the bottom of the river at 165 feet. From there, the current carried us along the flat bottom swiftly without us having to swim. My main concern was narcosis, as I hadn’t been anywhere near that depth before, so I forced myself to concentrate on the dive, looking around me, then at my gauges, then my watch, and back again to keep my brain in gear. It must have worked, I didn’t feel any effects and felt in control but not slaphappy.

Well into the dive, we came across a large anchor wedged between the wall and the bottom. We held on to it for a little while, regrouped, and then let the current carry us once more. Brad was leading the dive up front and started to do somersaults while zipping along 10 feet from the bottom. I tried to stay reasonably close to Pete, and Dave kept back a little.

After 25 minutes it was time to ascend. We hadn’t reached our destination which was the wreck James B. King, but the time was up so we had to make our way up the zebra mussel encrusted rocks to our first deco stop at 90 feet. The deco software we used was a Buhlmann model with gradient factors that mandated short deep stops, so there were 9 different depths on the tables. The hardest thing was moving from stop to stop in the current. We hid behind rocks the best we could but often we just had to hang on and wait it out. I also found I couldn’t read the tables on my wrist and to read the ones on my fin on some stops I had to twist into uncomfortable positions to get a line of sight on them.

Dave has a reputation of yelling intelligibly under water, and  when I was trying to find a better place to hang on I busted my 40′ stop by a couple of feet. I could hear him yelling “40 feet, 40 feet” at me while I scrambled back down. By this time we had switched to the EAN50 to shorten our deco time, but it was still a long haul. I couldn’t get my computer to switch over to Nitrox – the Apeks Quantum switches manually under water but you need to hold button A down for 4-5 seconds to make it stick. The other problem I had with the Quantum is that you lose the dive time once it goes into deco unless you press button B, so I used my dive watch and did it the old fashioned way. I started worrying about whether I’d bumped the bezel. In no-deco diving the ratchet on the watch bezel is a safety factor to make sure you don’t stay down too long, but on deco you need to stay as long as required, so the ratchet doesn’t help.

The rest of the dive was uneventful. The 20 and 10 foot stops were long, and by the time I reached the surface the current had chilled me down and I was shivering. My 3mm wet suit with my dry suit hood was just barely enough for the dive. Fortunately the boat was along in about 5 minutes to pick us up, and the day was hot so I was soon warmed up. My computer locked me out for 48 hours because it computed a longer 10 foot stop than the tables because it hadn’t taken the EAN50 into account, so I had to wait 2 days to review the log. I had 1000 PSI remaining in my doubles.

All in all, it was one fantastic drift dive that I would do again and again. It was also the last dive of my DSAT Tec Deep course.  I’m looking forward to another couple of shots at it this coming summer.

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