To simulate the storm in the Atlantic, a model of the tower was splashed with water from a large tank. Actor Jan Fedder lost his grip on the railing and was washed off the model, breaking a few ribs in the fall, one of the other actors instantly shouted "Man Overboard". At first Petersen didn't realize it was an accident but enthusiastically yelled "Good idea, Jan. We'll do that one more time!". Peterson still kept the scene and rewrote Jan Fedder's part in the film, so that his character spent a short portion of the movie in bed. The actor actually had to be brought back and forth from the hospital every day because of concussion. The painful expression on his face is real and not acted. (The scene which features him bedridden is available on the uncut edition.)
The cast was deliberately kept indoors continually during the shooting period in order to look as pale as a real submarine crew would on a mission at sea.