[Hitman]

Das Boot is of course very accurate in most things, howevere certain things needed be acommodated to the filming technique, like f.e. the blue lights -which never were on a real german WW2 U-Boat- Petersen said in the comments of the Director's cut version that those blue lights were used to make a more dramatic efect, making faces even more pale and ambience darker during the most dangerous moments, so as to set a bigger visual difference.

About the hatches: The watertight hatches are in all warships as a mean of being able to isolate damaged -flooding, burning- compartments, helping stop the flooding extend all over the boat or suffocating fire. In surface battleships they are mostly closed when at battlestations -Steve can sure give more precise details- but I must confess that I have no idea of what was done in submarines. From what I have readed, it looks like US submarines did not close them at least in the control room and conning tower while at combat, as I have readed several accounts of plain voice communicating between compartments and even glancing down through the hatch. I suppose it is more or less logical, because a submarine is smaller than a surface warship, and with much less compartments, so they can react quicker and more effectivier to emergencies.

Given the internal distribution of compartments in german submarines, I would bet that the hatch was open between control room and radio as well as to the conning tower. Probably the engine room and torpedo rooms had them however closed, as communicating was done through speakers due to the distance.