Corrected entry: Why is it that all Submarine movies have the obligatory flooding scene, yet no one ever does the math on how much force it takes to close a hatch after the compartment is flooded. In the scene in question there is flooding in what is known as the "Snake Pit" on submarines. The sailor tries to save his buddy but finally has to close the hatch when his shipmate cannot get out in time. Unfortunately, everyone should die because of this error. Mathematically the hatch, which on my sub was 28" is too big to be able to close against sea pressure, Area of a circle is: pi times r squared so; 28/2 = 14, 14 squared = 196, 196 times 3.1416 (pi) = 615 sq.in. Sea pressure at 100 feet is 44 pounds per square inch so 44 times 615 inches is 27,060 pounds of force on the underside of that hatch. Divided by 2000 pounds per ton means that that sailor, who successfully closed that hatch in the movie, must have weighed over 13.5 tons.
Correction: I agree, flooding seems to be a required staple in too many sub movies. But its dramatic effect cannot be denied. It works. In this example, Lt Hellerman single-handedly nearly dooms the whole boat. By failing to man-up to the urgency of the situation and take the required action, he waited till water started overflowing the hatch coaming. In a real-life situation, it would still be easy to close the hatch before water rose to that level. But unlike air, water is not compressible and will have the same hydrostatic pressure as the seawater at that depth, which was shown to be 1753ft. At that depth (53 ATM), the pressure on the 28" scuttle would be about [ (1753/33) +1] x 14.7 x 618 / 2000 = 246 Tons .
Correction: The pressure calculation should be done on the opening of the hole in the hull, not the opening of the hatch. The pressure at the hatch can only be as high as the pressure at the hole in the hull. There would still have been air in the compartment he was in, and that would absorb some of the pressure.