Continuity mistake: When a scuba diver (Pilar Seurat) approaches the flying sub, her regulator is on the left and her dive knife is on her right leg. Also, she activates the underwater voice transmitter with her left hand. Once aboard the flying sub, her regulator is on the right side, with the knife strapped to her left leg. Also, she's right-handed. The film of Seurat - more likely her stunt double - swimming towards the sub was likely "flipped".
Voyage to the Bottom of the Sea (1964)
1 mistake in The Silent Saboteurs
Starring: Richard Basehart, David Hedison, Del Monroe, Robert Dowdell
