The attempted robbery obviously occurs during early afternoon, but the Queen Mary is seen in early evening sailing away from the site. She should have been long gone by that time,
When the Queen stops, she should have exhausted most of her steam pressure through safety valves. Nothing is heard of this.
The Queen's whistle heard at the end of the movie is wrong. Her whistle was much deeper.
The German Type II submarine is missing the 20 mm anti-aircraft gun mounted on the conning tower. Also, the type II never operated in the Caribbean.
In some of the diving scenes, the back wall of the water tank used is clearly visible.
The treasure hunters find the skeletal remains of the U-boat commander inside the sub. Sealed inside a dry, airtight environment, the body should have mummified rather than being reduced to a skeleton.
The U-boat is shown using only about a dozen typical car batteries. It would take nearly 100 such batteries to equal just half the battery capacity of a small Type II U-boat, which had a full capacity of 7-8,000 Ah.
When the submarine is beneath the Queen Mary and the liner starts her engines and propellers, a technician's hand is clearly visible shaking the stern of the U-Boat model back and forth in the prop wake. This may not be apparent on the pan/scan version, but is obvious on the new Blu-Ray hi-def transfer.