pilot fish:
Two divers, buddies, are at 120 ft and both out of air, for whatever reason?
I'm not sure if this was directed at me or not, but I'll answer....
What you're describing is the most easily avoided "nightmare" scenario.
There is *no* reason that *anyone* should *ever* have to deal with this.
I've seen you bring up this scenario many times so I'm assuming this is your own worst case scenario. With all due respect, I don't think it demands serious consideration. In terms of dealing with this risk, avoidance is so easy that long discussions over contingency to deal with it are kind of pointless.
PF, think about risk like this. There is a ladder of ways to deal with a risk:
1) avoid
2) contain
3) contingency
4) transfer
5) accept
#4-5 aren't relevant in diving. #1-3 are the preferred ways of dealing with risk in the order of priority
1) avoid - check gauges, plan gas
2) contain - use a pony or other form of redundancy to ensure that the event can be delayed or the effects minimized
3) contingency - think about CESA's, DAN insurance etc.
4) not relevant for diving
5) unwise and unnecessary and therefore also not relevant for diving.
I'm sure we've pointed this out to you before but somehow it doesn't want to sink in. You're stuck on thinking about #3 but in order to even get that far, you ignored two other very viable and effective risk mitigation strategies....
Please do reflect on this for a while, it can bring a lot of peace of mind if you look at your risk management like this. Really.
R..