We'd heard the Devil's Throat was very cool and talked to the operators about that. They said there was a group of 4 who also wanted to go, but since it's 130' and a swim-through they wanted to take us all for a deep check-out dive first, which we all went off to do on Columbia Wall with a different DM, who I'll call Gabriel to not protect the guilty.
Gabriel preps us by saying we'll go to 130' max, come up when you have 700 lbs or all together after 20 mins. Everyone in the group is diving on a computer. Since the PADI charts say 10 mins at 130' I'm trusting two things 1) that the computer will say when we need to come up 2) that my buddy's going to run out of air before then anyway.
Gabriel tells us to meet him at 130' and goes in. We all follow and my buddy and I are going down maybe 10-15' away from each other. I'm looking at my gauge and see that the DM has passed 130' and I'm already at 135' myself. My buddy is following the DM and not looking at me, so I started wailing away on my tank to get his attention. Gabriel looks up, but my buddy doesn't. I've slowed my descent, but that means he's going away from me even faster.
So I'm thinking, he's not only my buddy but my good friend, and I talked him into all of this. I'm also the more experienced diver, so this is all my responsibility. So I keep going down to get him. I get to 159' and finally get his attention. He's at 162'. I give the emphatic motions for 1 3 0 and point up. He says OK, and we start going up slowly.
BTW, the others in the group have done a variety of things. One couple is up higher, looks like 130-135'. The other buddy team is not together - one's maybe at 145', the other is down with my buddy and the DM.
A few seconds later I turn around to check on my buddy and find that he's not coming up with me. He has gone back down with the DM. OMG, what's he doing?? I'm thinking he must be narked, since he obviously understood what I was saying about 130'.
So again I go off on the tank banger, and again Gabriel notices. He finally points that out to my buddy, who then finally looks at his gauges, shows them to the DM and starts coming up. He lets me know he's low on air, so it's time to go up. Good!
We go up and are having to swim hard to get over the edge of the wall due to the current. He's holding my hand at this point, making it harder to swim, but then he shows my why. At 80' he's got about 50 lbs of air. I have 1500, so we're OK there. I make him run out competely, we share my air, then we start start the slowest ascent I've ever made, since I don't know what you're supposed to do after 160'/170'!