How do you open the hatch?

[Akong]

You move your hand (mouse) over the hatch, and hold down on the left mouse button and move the mouse up.

It can be a little tricky in the beginning. I think I had problems with it too, which was made infinitely worse by the fact that I was slowly dieing. It all worked out in the end, though, and contributed to a more tense and suspenseful sequence.

Edit: When I say slowly, I of course mean very rapidly.