Ok, he's goin to turn off my air? and I'm to do an e.b.a?

[dpbishop]

Back in '83 we had to do this for Basic Scuba Diver cert.!
We had an instructor that would constantly sneak up behind you (not hard in a pool) and shut off your air. After the first time, it was no big deal. Make sure your instructor knows you're worried so he/she will walk you through it.

Back in the sixties I was working as a lifeguard at the pool in the Pentagon. (yes, they have a pool) As a final exam for their Basic Scuba class, the instructor blacked out the students masks, then free dove around them, turning off their air and pulling off their fins. You weren't supposed to surface until you had all your equipment on.

The final for the lifesaving class was even more sadistic.

 

[Gombessa]

I can't recall ever breathing down my reg until I had to do a v-drill. But doing so on the land (with a mask on helps, even if you're not in the water) is a great way to get an idea of what the feeling is like.