I've been reading this ongoing thread with interest, and have to comment coppermaus for inviting advice not only once, but twice. You are either thick skinned or a glutton for punishment. You?ve already received some good comments along the lines of what I would have offered; most of what Walter said echo my own thoughts. I also agree with what Crispos said about needing to offer to share air sooner, and would like to add my 2 cents worth. In my experience, it has been such a common experience for my buddies to consume air at a much faster rate than I, that I have developed a protocol to deal with the situation in a way that seems to work well for both me and my buddy. Before the dive, in the process of discussing our dive plan, we talk about what our turnaround point will be for the dive based on a mutually agreed on PSI level. I tell my buddy I will be checking with him periodically to ask his air level, and if when he reaches the ?turnaround? psi level, if I still have substantially more air, I will at that point offer to share my octopus with him so we can continue the dive until my air level is closer to the turnaround psi, at which point he will go back on his own air supply and we will then turn around. I go over how he should best position himself while on my octopus; usually recommending he position himself above my right shoulder and slightly behind me with his left hand resting on my tank valve to prevent me from dragging him along by the octopus in his mouth. This way we both get to extend our dive a little longer, we both get a chance to practice sharing air in a relaxed, non-emergency situation, and we are both left with enough air to deal with the rest of the dive and any difficulties we might encounter on assent or exit. I?ve found that trying to share air with someone on assent and exit is asking for trouble should conditions get rough on the surface, etc, especially if my buddy doesn?t have any air left in his tank as backup. Of course, all this necessitates that you are first confidant of your own skills and comfortable with someone breathing off your tank, etc. But I would repeat that it is much better for you to practice sharing air under controlled circumstances than in an emergency, so you will get comfortable with the concept and not view it as something only used in case of emergency.
I commend your attitude regarding wanting to inform the operator of the incident rather than spread harmful details behind his back. And as you said,
?it's a situation any of us could find ourselves in going with ANY op. If we avoid Shop X at all costs, don't we just have a false sense of security? Sure, the DM was unreliable, but since I did not talk to the dive op about him, is it fair for me to talk about the dive op to the world on SB? Because so many of people want to know their name, I realized it's my responsibility either to tell you or to tell the dive op about Gabriel, so they can deal with him, which is what I'm going to do. I truly do think they are a very good operation, so they do need to know about this guy's unsafe behavior. HOWEVER, any shop could have a DM that doesn't realize his depth gauge is broken and goes down and down and down. He's not an instructor; we all have our c-cards and shouldn't be relying on him anyway, right? The important thing to know is NOT to follow the DM blindly. ?
As Knives and @BAR said, you need to be confident in your own skills and able to rely on yourself, not your buddy or the DM, to deal with any situation. You also need to be assertive about not exceeding your training, skills and comfort level. As others mentioned, these are issues you need to talk with your buddy about before the dive; as in, whether you are willing to risk your own safety and stick with him if he is doing something stupid.
The question is, what would YOU do in that situation? Would you - or your buddy - follow him? Or would you dive your plan and stick together? If your buddy went, would you follow to "save" him/her? Or would you stay where you're supposed to be and deal with whatever falls out? When you're at 130' the brain seems to work slower, so it's good to know these things before you go. And good to know your buddy's answers, too, so you know what to expect from each other.
Several of your comments, regarding ?it?s a situation any of us could find ourselves in? combined with what you said about not knowing how to do deco stops, and your desire to learn decompression diving brings up another pet peeve. Encountering a situation where you exceed the recommended maximum no decompression limits IS something most divers will eventually encounter. Unfortunately, most dive training agencies emphasize no decompression diving so exclusively that when a diver does ?go into deco?, they are prepared to do only one thing: panic! Rather than train divers to be paranoid about what is sooner or later an inevitable situation, I really feel some basics regarding decompression dives should be part of any advanced level training. After all, shouldn?t the purpose of the training to be to help the diver be prepared for whatever situation he encounters, and how to properly execute the necessary skills with the comfort that comes with knowledge and training, rather than leave him to figure it out for himself at his own risk?
Which brings up one final point. It was good that you added a few minutes to your safety stop, but I would suggest it would have been better, knowing you HAD exceeded the no decompression dive limits, to add more like 10 minutes, since at this point you were NOT doing a safety stop, you were doing a decompression stop.