The triple-tank aqualungs used by the UDT frogmen during the film's climactic mission are incorrect for the WWII period. Although 'Jacques Cousteau', an officer in the French Navy, was working with experimental aqualungs near the end of WWII, U.S. Navy Underwater Demolition Teams did not have them during the war. Re-breathers, which had filters to trap carbon dioxide, were in use during this time period. Modern SEAL type units still use re-breathers because they produce no bubbles which can attract unwanted attention like they did in the movie. The Japanese divers in the movie had bubble-less re-breathers.
In most above water close-up shots, the men wear their face mask on their forehead. This is photogenic, but a good way to lose a mask. To keep the mask from falling off, it should be pulled down below the chin. This is most notable in the speed boat drop-off and pick-up scenes.
About 20 minutes in when Lawrence scratches his leg on the coral we see blood squirt in the water. A few moments later the gash on his leg is shown, but there is no blood to be seen. Due to the size of the wound this is just not possible, there should be plenty of blood visible.
After the torpedo hits the team's ship, the XO determines that they can't enter through the door as the water level in the compartment is too high. He says they'll have to "go in through the manhole in the overhead." The proper term would be to enter through the scuttle in the overhead.