Something rather annoying that happens is aircraft exploding after they submerge, now unless someone is setting off explosives inside the aircraft or pressure is building up in the fuel tanks somehow this shouldn't really happen, sure the engine, instruments, etc should be damaged... but the problem is the hull also gets damaged fully, which causes the aircraft to explode underwater, killing its occupants which have a very, very, thin time-frame of which to escape the helicopter where realistically, they should have as long as they want until they drown.