The air pressure needs to be able to flow both ways. Before I had a hole in my bulkhead, I once opened my hatches (held with bungie cords) on a hot afternoon then paddled on very cold water. The air beneath the hatch contracted so much that it took two of us pulling as hard as we could, just to get the hatch cover off. I've never seen it happen, but have heard stories of decks collapsing as the air inside cools and contracts.

John

: Brian, the 1/32" hole in the water tight compartments sounds good to me
: but with a piece of duck tape over it. That would keep water from getting
: in from the outside but if the pressure built up too much on the inside it
: would loosen the tape and escape

: John