When Johnny and Dominic are showing their finds to Theresa, the mug-shaped object appears on the table a few seconds before Dominic lifts it out of the bag.
When Richard Egan, Gilbert Roland escort Joseph Calleia and his two friends from their boat Robert Keith is in a black jacket, shirt and dog collar and is about to go to bed but when they return he's now dressed in an open neck brown shirt and trousers.
Johnny's narration as they sail to the wreck site includes the following " ...when evening tossed out the stars like shining dice, I could only see the high-priced bangles that hang around Theresa's throat." However Theresa does not wear necklaces when she is on the deck and only once when below.
When the boat is blessed, there are people and vessels in the background as seen from a high angle shot. These vessels disappear in the low-angle shot, even though they had masts, etc which should be visible.
Toward the end of the movie, a rope was tied around a large piece of wood that trapped Jane Russell. It was never untied and should have pulled the winch overboard when that part of the wreck broke off and sank further.
The ship that that Johnny (Richard Egan), Dominic (Gilbert Roland), and Theresa (Jane Russell) are exploring sank in 1640, over 300 years earlier. A wooden ship such as the Santo Bello, exposed to seawater for over three centuries, would have rotten away by the mid-1700s. The ship in the movie is in too good of condition to be a 300-year-old wreck.
At the beginning of the film, Richard Egan's voice-over twice specifies that the gas in his SCUBA tank is "oxygen." His tanks contain compressed air, which is approximately 79% nitrogen and 21% oxygen. If they contained pure oxygen, the diver would likely experience oxygen toxicity and go into convulsions within a short period of time at about 20 feet, and even more quickly at deeper depths. But oxygen is the part of air that keeps us alive, and without wanting to give the audience a science lesson on oxygen/nitrogen ratios, calling it oxygen instead of air is natural. Also, his words were "... you'd sure eat up the oxygen..." and "... oxygen enough to stay down...," neither of which implies tanks of pure oxygen.
When the shark hunters come about the "SANS SOUCI" towards the end of the film, it is clear this shot is actually shot in reverse. The life preserver shows the gold lettering as a mirror-image. This was probably due to the fact that the boats were in the opposite direction while photographed in the ocean and were flipped when photographed on the studio set. They had to show that particular take in reverse for the sake of continuity. The name of the boat "SANS SOUCI" means "carefree" or "without worries".
When Theresa pushes Johnny off the boat at the end, the walls of the tank in which the boat floats is visible in the background.
Hairy-chested Gilbert Roland's underwater stunt double is bare-chested.
Richard Egan and Gilbert Roland set off an underwater explosion to blow the door off a strong room of an old ship. The ship, which is balanced on the edge of a reef, shakes and a large piece pf the reef breaks off but Jane Russell, say on the edge of a hatchway doesn't move.