I'm only posting this because this is a requested "no-flame" thread.
Once upon a time.
I met a new potential buddy online and we chatted for a bit and figured we wanted to go diving, check each other out. We carpooled up along the St.Lawrence River in Ontario (since it was local to us) headed for a nice easy shore dive site. However enroute, we got to comparing (dive) notes and realized we got a kick out of the same kinds of dives. Somewhere along the way the plan changed to include Lock 21.
Lock 21 is up near the Lost Villages which were flooded to create the seaway. This is an area of stiff and variable current and typically low viz.
So here we have:
1. new unfamiliar buddy
2. stiff current
3. low vis
4. on the edge of a commercial shipping channel (the St.Lawrence Seaway)
Moreover, as I had been transitioning to double tanks for a bit, this new buddy was loaning me his double steel 72s.
5. unfamiliar gear
And I had dived the site before, but only with other buddies who were intensely familiar with it.
6. relatively unfamiliar site; buddy's never been there either
Oh yeah and I'm wearing my drysuit which I still had less than 20 dives on at the time, if memory serves.
7. more unfamiliar gear
So we gear up and go over the plan. There's a buoy you can swim to that marks the upstream edge of the lock face, and several permanent lines at various points along the weir and leading to the downstream exit. But the last time I had dived the site, my (knowledgeable) buddies had decided to enter at the downstream end, pull-and-grab along the weir bottom til we reached the lock face, then drift back downstream again afterwards for the exit. This plan seemed to work very well, so that is what we would do.
We get in the water and I discover I need just a bit more weight. We get out, I add weight, we get back in. We descend into a rather stiff current (hm, the river's "up") and begin our trek down to the weir. We're following the permanent guideline and all is good.
What's this? The end of the guideline? And no sign of the one that parallels the weir's edge. Well, no problem, we'll just pull upstream til we hit the lock face.
8. the dive site differs from plan
We begin the pull and glide, buddy gamely following me (I'm leading, of course, because buddy's never been to this site) I check my SPGs and switch regs. Oh, I forgot to mention these doubles were not manifolded, so they're breathed like sidemount tanks, switching from one to the other tank every so often to use the gas evenly.
9. less known gear configuration requiring additional task loading
We continue pulling and grabbing as the current seems to slack off. In fact, it's almost still. Odd, because at the foot of the lock face are three huge sluice gates that divers like to shoot through, so we should be feeling strong currents. Uh oh, not the current's pushing me! Quick, check the compass - uh oh, it's swinging to point at every piece of metal or iron rebar buried in this place.
10. Lost!
I see something up ahead - a dark blurry shape in the murk. I swim over. It's a wall. Phew. Okay, follow this upstream. Swimming, swimming... it STOPS. What the heck? I turn to look at buddy - he's showing me his SPG. It's somewhat less than 1000 psi!
11. buddy running out of gas.
And I check mine and realize I missed a gas switch along the way. I switch over to the other tank but they're a bit uneven now. Mind you that's minor. We have to figure out where we are. Currents are swirling and there's no wall or reliable visual reference, and my compass is useless. I think about the current, the low vis, the shipping channel just to the south of us. And the fact that we dived off what used o be mainland but is now an island, after the flooding decades ago.
12. we dived off an island, so we don't want to drift away
Drifting downstream off an island in a current is not my idea of a good time. Buddy shows me his guage again. It's looking much closer to 500 psi now. (we're at about 35') I offer him one of my regs; after checking my guages, he declines just yet. I contemplate for oment, then clearly signal to him that I'm lost, and that our best bet is a free ascent, but that I wanted us to hang onto each other just in case, to prevent separation in the current. Reluctantly, he agrees.
We started our ascent, sure enough starting to be carried downstream as we left the bottom. At roughly the same time as each other, we both spotted a slope of ground and pointed it out - we swam hard back to the upslope which could only be part of the island! We pulled and grabbed our way up the slope, staying low and out of the worst of the current, until we were to the edge of the water and able to stand up.
We emerged about 4' from where we had gone in.
Afterwards, I discussed the dive with my buddy and admitted that I had gotten very very worried down there when everything started to more or less pile up. "I know", he said, "I saw your big eyes. But you were still thinking things through, you didn't panic. I'd dive with you anytime, anywhere."
Although, that doesn't mean I'd stack the deck against myself that way again. And I haven't.