Revealing mistake: As soon as the three survivors are coming out of the lab through the hatch underwater, they all signal each other to rise to the top. Look at Safron Burrows, her cheeks are full of air and you can almost see the surface above her head. You can also see the exact same shot when she is about to be eaten by the last shark. And what's with that hand gesture - to cut or for the shark to stop? (01:26:30 - 01:33:10)
Factual error: Near the beginning when the boat pulls up and the guy on the boat tells the blond convict he's got a beauty 13 foot "Tiger shark" that's up in some sort of sling, the so called tiger shark is actually the same robot mako shark from the rest of the movie, just with stripes on it. Tiger sharks have a blunt rounded nose, not a pointed one like a great white. (00:07:35)
Revealing mistake: In the scene where L.L. Cool J. is in the flooded kitchen and the shark comes in through the door, he climbs up a shelf, then falls in the water, then climbs out again. Before he makes his way to the oven you can clearly see that under his pants he is wearing knee pads. (00:53:35)
Continuity mistake: Near the end scene, when the three characters came to the surface, L.L. Cool J. was taken by the shark. When he was taken underwater and when he surfaced, the shark had him in her mouth on the right side. When they went under again and resurfaced, L.L.Cool J. was on the left of the shark's mouth. What? Did the shark not like him on the right side so she switched him underwater? (01:27:30)
Factual error: Since the water was always waist high, how could the huge sharks swim inside? Not to mention the corridors... (00:51:10)
Continuity mistake: The man with the cross has a wound on the left hand side of his head. Later in the movie it has moved down.
Continuity mistake: While Carter is trying to save Jan he is a few feet above the water. But in a shot from above you can see that he has to bend his body so as not to touch the surface. It would be very easy for him to reach her, then! But in the next shot, he's high above the water again. (01:06:25)
Continuity mistake: When Carter is sitting in front of one of the small hatch-like doors around the time that they were climbing the ladder to escape from the rising water, one can clearly sea that the door is no more than twice the width of Carter (4 feet at most) yet the 45 foot shark about 10 to 12 feet wide seems to have no trouble squeezing through. (01:01:40 - 01:04:20)
Continuity mistake: When Carter climbs the ladder to get out of the water after removing the licence plate from the shark's mouth, it shows a shot of his feet and he is wearing sandals. In the tank he was wearing swim fins. He talks to the big boss for a few seconds and the fins are nowhere to be seen. He then walks away with the fins in his hand. (00:08:55 - 00:10:20)
Continuity mistake: When the shark rises above water with Jan partially in its mouth, its teeth are in about the level of her waist. As Carter grabs onto Jan, it moves its teeth up to the top of her chest. In the wide shot that follows, though, its teeth are back at her waist, then in the last shot of her being pulled underwater, they are up way higher again, at her chest.