Other mistake: In the scene in which two Japanese Zero fighters bomb and strafe a PT base, shots of the attacking planes show them carrying no bombs. During the attack, they still drop around 20 bombs anyway, which is considerably more than the actual carrying capacity of the two planes.
Other mistake: When JFK meets with Australian coast watcher Evans, he tells Evans he only has three shots in his revolver. Evans gives him his rifle for the fourth recognition shot. That revolver should have held at least 5 to 6 shots. When did JFK fire the others? We never see that prior to that scene.