Submarine X-1Goofs

When Quentin drops the bolt cutters as he's trying to cut through the submarine net during practice, and the sub tries and fails to ram through the partially cut net, Quentin is briefly shown right after the sub gets stuck and he's still holding the bolt cutters even though he had just dropped them. He had no time to swim down and retrieve them as the cutters were shown dropping a good 50 yards when he dropped them.

The X Craft were only 5 foot 8 inches high inside but 6 foot men are seen standing upright with space to spare.

Throughout the early portion of the movie the X craft program is referred to as "Top Secret". At this point in time, the British used the term "Most Secret", Top Secret being an American term.

One of the German paratroopers appears to be carrying a Thompson submachinegun-an American weapon.