I have only dove one wreck, this one, off Snake Island in BC about 10 years ago. It was cold and dark, and scary as shit. My climbing (and diving and sailing) buddy was going down in a drysuit for the first time, and my (later to become) wife and I were in our 6mm "Puget Sound" wetsuits. Phil fucked up while airing up his drysuit at 15 feet down and upended himself and couldn't re-right himself. He freaked out and bolted for the surface (upside down). You should have seen his eyes, big as fuq'n saucers, as he missiled past me.
So now I'm waiting in the water while Rebecca gears up, since she wasn't originally planning on diving this wreck, but was waiting until we went to a mellow reef dive later that afternoon. As I mentioned in another post, she has way more dives under her belt than me, and is certified for wreck diving, but it had been several years for her since she last penetrated anything at this depth (100+ feet). So I'm bobbing around at the bow of the boat, using air because the sea is really choppy, and it's easier to breathe this way than swallowing seawater. I didn't bother to check my tank's gauge before she hopped in and we descended the anchor line together to the wreck.
The current was pretty strong at shallow depths, but as we descended into the dark, it abated and we drifted right onto one of the gun turrets. We let go of the anchor line and swam down to the deck, and at about that time, I checked my gauges. SHIT! I had about 700 lbs of air left! And I had a 100+ foot decompression to go through still. For those that don't know what this means, you start a dive with around 3,000 lbs of compressed air on your back, and you aim to be back on the boat with about 1,000 lbs still in the tank, for safety reasons.
I signaled to Rebecca that I had to go up, and now. She was confused, until I showed her my gauge readings. Then her eyes got as big as fuq'n saucers, just like Phil's had, but for a different reason! So we swam around for a few more minutes, burning up my dwindling air, until we found the anchor line again and began our ascent. Stopped at all the right places on the way up (the line is permanently marked with deco stops) but had to guess on the time. That was because Phil had the only dive watch in the group, and he was sitting topside, de-freaking out. So it was a tad bit unnerving, trying to guess how long I was at each stop. I learned how to count time pretty well that day...
Anyway, I put Rebecca in the boat first, and when I got in and had a chance to relax, I checked my gauge. I had about 100 lbs of air left, at sea level. I had never gone that low on air before, and I was pretty alarmed, but glad to be on board. Everyone else on the boat, including the charter captain and another pair of divers (them bastards had nitrox :jealous: ), were more excited about it than I was, and congratulated me on how cooly I handled the situation. I was just happy to be breathing real air. Between my being dangerously low on air and Phil's freak-out, I realized after that dive just how easy it would be to get hurt real bad while diving if you didn't keep your emotions in control. We motored over to the second dive spot of the day, and we contented ourselves to dive a reef at only 35 feet. The resident octopus (who is very friendly and well-acquainted with divers) came out and climbed on my head. Much less stressful than diving the wreck...