Should this be behind an LJ cut? Just to keep the front page neat ... :/ Maybe it's not long enough for that but it was my first thought.

I rather enjoyed reading this, although it might be better if we could see what he was threatening her with. You say he wouldn't let her just pull herself out of the pool, but what's stopping her? There should be some visual incentive to keep her there, because really, if you knew you were going to drown by staying in the water, you'd be inclined to get out unless there was a gun held to your head or something, and even then you might well risk it.