Continuity mistake: In the opening scenes, when David is chiding Gail for grabbing him through the porthole of the wreck, his right hand is gloved, then ungloved, then regloved..all in the space of a few moments.
Continuity mistake: When Treece's air line gets caught up with sharks and he is dragged out of the wreck, the only thing to hold onto is a metal bar that is attached to a metal plate, but when David and Gail arrive with the suction device, suddenly there is a whole lot more going on on the sea floor, including a perfect hole to put the suction tube in, so they can turn it on and, after cutting David's and Treece's air lines, they can rise to the surface, hidden from the sharks by all the air and rubbish from the suction tube.kh1616
Continuity mistake: The first night David and Gail spend at Treece's, Gail walks into the bedroom with a glass of rum in her hand. David is in bed, sitting up, topless. Gail sits on the bed, David moves down and starts kissing her back through her clothes. She lies down and he pulls her up the bed and turns her over - the glass of rum has vanished.kh1616
Revealing mistake: At the beginning, when Gail is attacked by a moray eel - we don't see it, but that's the assumption - and she is banged against the sunken wreck of a ship, and then, when she is released, her mouthpiece is not in her mouth and she tries to swim to the top as fast as she can - all of this is done by a stunt double, understandably, we can see this by her hair, which is much thinner and straighter than Jacqueline Bissett's hair.kh1616
Plot hole: If the vacuum is strong enough to suck up a hand grenade, why isn't it sucking up the ampules?