Factual error: The shark follows Brody into the sunken ship (yeah, right) and eventually the chase ends with the shark at the end of a very narrow passageway, with no room for it swim further forward, and no room to turn. Since the rigid nature of a shark's pectoral fins means that they cannot swim backwards this one would be stuck. And since Great White sharks have to constantly swim in order to breathe, the movie really should have ended right there.
Revealing mistake: During the sequence when Michael has his underwater motorcraft and the shark attacks him, you can see in certain long shots the machine which works the shark protruding from under its tail.
Continuity mistake: In one of the final scenes in which the shark is attacking, the colour of the water is not consistent in the background. In one scene it is light blue, and in the other it is much darker blue.