Yep Matt, that would really suck. Was that Cozumel by any chance? The outfit we dive with there pairs everybody up so if one runs out of air only the pair has to surface.

Twanger, it mostly just happens. I watch the dive masters too and I've noticed they keep warm (wetsuit and hoods), have loooong fins (don't use their arms much) and no wasted motions, oh and they're almost always skinny and very fit! Of course, we recreational divers will never get as good as someone that dives almost every day.