Thursday, April 27, 2006

Trimix dive

Jamie's found the HTMS Pangan's officers mess and is planning a treasure hunt together with Stewart. Michael's spotted some brass port-holes ready to be hammered out of the wreck's rusted steel hull. My plan is to get further acquainted with the wreck and shoot some pictures of the encounter. The sea's almost as flat as a mirror, reflecting the few clouds in the sky. With a bit of luck the viz won't be too bad. While the crew keeps diving on free air, I decide to go on expensive trimix. After two days of diving on air I'm still getting pretty narced. And while I do think it's a great 'Shadow Divers'-like experience, I would like to remember a bit more of my dives.

Batteries recharged and the camera carefully replaced in its waterproof housing, I'm ready to get seriously wet once again. But first I need to analyse the gas in all my tanks, a precaution not to be neglected without potentially fatal consequences. Satisfied with the oxygen percentage readings, I then suit up and strap on all my gear.

↓ 5m. My trimix being hypoxic, I breathe nitrox for the swim to the down line and for the initial descent, only switching to my trimix back gas around 5m where it's safe enough. Nitrox regulator stowed away, I wet my camera's wide-angle lens, pressurize my oxygen tank's 1st stage and check all my instruments: depth & pressure gauges, dive watch & computer. 10m. Lots of things to think about & do when beginning the dive. 15m. 20m. All the while sinking deeper and deeper, equalizing regularly and monitoring my breathing, as there's a bit of mid-water current and I actually need to pull myself down along the line. 25m. 30m.

↓ 35m. The wreck's already clearly visible, at least for my twilight adjusted eyes, parts of its structure sticking out mysteriously from the silt cloud enveloping it. 40m. Jacks are circling around and around on top of the wreck. 45m. I inflate my wings to brake my descent.

↓ 50m. There's no current on the wreck. Cool. I take my bearings, unhook my camera and head off. Thanks to the trimix, there's only a hint of narcosis - and that probably only because of the task loading. So my head is remarkably clear compared to my previous air dives. And the viz is good enough that I don't need to use a reel. Unleashed, I'm free to wander about at will. Having planned for a max-depth of 60m, there's no risk of me dropping too deep, unless I start digging. Still, I constantly monitor my depth, time & gas consumption.

↓ 55m. The wreck's covered in silt, clams and fishing nets. It's pretty hard to recognize any detail from or object belonging to the old ship. There're plenty of swim-throughs and drop-ins, and this time I do venture inside, keeping in mind that entanglement is a real hazard here.

Every now and then I stop and try to take a couple of pictures. The ambient light however is barely enough for snapshot photography and lots of the shots come out blurry, but some are acceptable and will do as souvenirs.

Soon I've almost used half of my back gas. Time to find the ascent line again.

Having a fixed line of ascent is really a great advantage not to be underestimated. The alternative, a blue ascent with SMB deployment is always a risky business. Currents might take you for quite a ride, requiring patrolling chase boats with an alert crew on the look-out for your SMB. Especially in heavy seas. SMB deployment is an art in itself. If something goes wrong (read: your reel jams) you might end up being jerked up by the buoy accelerating towards the surface. Thereby potentially breaking one or more deco ceilings.

↑ No worries here however as I slowly, hand over hand, climb up the anchor line. Switching to my deco gas as soon as I can. As the current grows stronger in mid-water, all I have to do is release my tight grip just a bit in order to be pushed up along the line like an elevator to my next stop. Cool, but tiresome. Each time I move up I also release some gas from my wings to remain neutral. I try to focus on one stop at a time, not thinking about the total remaining time to surface. Keeping an eye on both my timers. Minute by minute. Staring into the blue. Down the line disappearing into nothing. Watching plankton drift by. A sea snake undulating its way down again after having taken a fresh gulp of air. Changing my grip to avoid tension build up. Watching rising & expanding bubbles from divers somewhere down below.

↑ As my 9m stop comes to an end, I turn around and let the current push me towards the deco rig, making sure I maintain a level depth. With more than half an hour on pure oxygen, it's good to have it surface supplied. Though I do carry an oxygen tank, it's only meant to be used in case of an emergency (read: blue ascent). Surface supplied does mean somebody up there must keep an eye on the supply! With up to four divers decompressing at the same time, even big surface tanks do get sucked empty, in which case a fast switch to a new tank is required. Pure oxygen is strong stuff, so after about 20 minutes I temporarily switch to a lower oxygen percentage for a so called air-break. A couple of squids are hovering nearby. Distracting me from the endless wait.

After almost 90 minutes of decompression, I finally resurface, with a camera full of snapshots. Jamie & Stewart come up with a bag full of china. Michael loaded with a heavy brass port-hole. Mission accomplished. As you can, I hope, tell from the pictures.

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