Continuity mistake: When the Master Diver is preparing to go under water to take the final exam, he is shown being fitted with a brass helmet with a window on top. In the next shot as he is descending the ladder into the water, there is no window.
Continuity mistake: When Carl is diving to retrieve the lost nuclear bomb, the Soviet submarine crashes into his air hose assembly and it gets caught in the bow dive planes of the submarine, which is accurate, since all Soviet submarines, including those of the era in which the movie is set, are designed with bow planes. Once the cables work themselves free, we see the submarine sailing away, its dive planes are mounted on the conning tower, which is where U.S. submarines during the 60s-90s had their dive planes mounted. No submarine is equipped with both bow and conning tower dive planes, so the conclusion is that the movie-makers used a model of a Soviet sub for the "tangling" and "dragging" shots, and a model of a U.S. sub for the "sailing away" shot.
Continuity mistake: When Sunday pulls up in a car to speak with Brashear, there is a prominent red streak on the door in the back seat. In the next shot, it's completely gone.
Continuity mistake: When Carl Brashear in the courtroom is walking with the 130kg heavy diving suit, he is taking the last step against Leslie Sunday. When he has taken the step he moves his left foot one more time as easily as if it was a pair of Nike Air shoes he was wearing, but earlier he almost couldn't take his 9 step.
Continuity mistake: When Sunday wakes up Brashear and blasts him with a hose, his shirt is rolled up to his armpits. Then when Sunday picks him up it's rolled down.