[SabreHawk]

Well this isn't a bug, shift+U is intended as a workarund for something entirely different where the player gets stuck and cannot move.

What happened here is using it for something for which is was never intended, and the player paid the price for being too impatient to get back to the control room and wound up somewhere else. And he did it while in the worst of situations.
What happned next was the game simply doing what it's supposed to do, which is not to allow the hatch to be opened while submerged.

I think he has taken it with stride though, and made a funny story of it, so good on him. Im sure he wont do it again, thats the good thing about learning things the hard way............you are quite a bit more likely to never repeat it.