Sea survival training in larger airlines usually involves a slide raft, and a public swimming pool, usually after their closure time.
+1 for us, and in our case that is/was only done once, on initial entry training ( IMHO I don't think that's adequate, but that's beside the point).
So in terms of hurdles to becoming a airline pilot there are much more important things to think about. Routine and frequent sea survival training is probably only a big factor for the military or possibly helicopter flying.