Corrected entry: During the climax, when Top turns on the air flow from his tank, he holds the pressure gauge in his hand so that the face of the gauge is pointing toward him. In fact, you are supposed to point the face of the gauge away from your body, so as not to cause injury if it the glass explodes. No experienced diver would make that mistake.
Corrected entry: Since a cave is a closed environment, you never use flares or any similar burning device inside a cave because it will fill it with smoke. That's a basic caving rule.
Corrected entry: Throughout the movie the characters are talking to each other during their dives, yet they all have regulators in their mouths.