The survey team diver who is pulled up into the ship first is at varying levels of climbing out of the water in successive shots; sometimes higher out, and then lower down later on; he is also twice reached down for by the crew.
The number on the sub reads "686" in the beginning portion of the movie, yet when it is shown hitting the sea-floor, the number is "509", the same as the U-boat in U-509 (1977).
The lady merc is seen holding a dimly-lit flashlight a moment before she flashes it to attract the sharks so they will attack the shark cage, yet in the next shot, she is using a flashlight that flashes brightly and goes out completely between flashes.
A different shark is used in the wrestling scene; it is much smaller than a great white, is brown instead of light gray, has a shorter broader shape and blunter snout, and has no visible teeth.
Too much air is shown escaping from the sub to have been contained inside the relatively small hull; the tiny model sub has a hidden air-hose attached is feeding a continuous supply of air to the model so that it can emit a steady stream of bubbles..
When the shark-cage cable snaps, there is a loud echoing "in dry air" crashing sound, whereas a breaking cable underwater would just produce a brief muffled pop.
When the hydrophones are dropped, the silhouette of a submarine can be seen in the near background.
The canned-goods delivery man is seen to be peeling off the backing from the transmitter's foam-adhesive mounting-pad, yet in the next shot of him arming the transmitter, he does not stick it onto anything, but merely places it on top of the horizontal molding underneath the comestibles shelf.
The depth below the sub a few seconds before impact is stated to be twenty feet, yet the picture shows the sub in empty clear water, with no visible bottom below it.
Steve says he didn't hear an explosion, yet there is a very loud jolting bang when the bomb goes off. In such a small submarine, anyone would have heard the detonation.
The merc reports that the main hatch is secured, yet Steve swims down and opens it without turning the latching-wheel, indicating that it was never secured from when he and his buddies exited the sub during their escape some time earlier.
Oscar says he doesn't know if the munitions thefts and the present situation with the downed sub are related, and yet he then says that the sub is now armed. He still could not know if the stolen weapons had been loaded onto the sub.
The lady merc has a simple push-to-transmit (not VOX) walkie-talkie, and she presses the talk-button to ask if her father had heard what the older merc had said, so the father could not have heard the older merc's estimate about how long it would take to rig a replacement steering system.