Signalling air remaining when diving with single tank divers.

[Paul S]

I'm surprised I haven't seen this, but if I'm diving 2 tank side-mount in a recreational situation, where most people are diving single tanks, I signal a single figure. I treat the 2 tanks as one, and just average out the numbers. That would then be a similar figure to what I'd be signalling if I had back mounted doubles with a manifold. I do that because it means I'm not overloading the other person with information, so they're more likely to register what I'm saying.

I have found myself tapping a cylinder and signalling what's left in that one, but normally that's because somebody is getting jittery about the gas they have left. It's more of a "Don't worry. I've got plenty of gas for you". Just the other day someone I was diving with looked at their gauge and it was moving as they breathed. Someone had "switched on" their gas without them knowing on the boat, but it was already on. "All the way on and half a turn back" was "nearly off". We sorted the situation underwater, but it freaked them out and they then didn't trust the gauge any more. Saying "This 3/4 full tank is yours if you need it" can be comforting and help bring a situation under control.

Of course, had they been in side-mount they could have tested and opened the valve themselves.