Continuity mistake: When Dan walks down to a podium and looks over to see the dolphin knocking at the gate, the tee-shirt he is wearing changes from being plain white with a tag badge on his left, to a white shirt with a large blue stripe across it, with a tag badge being on the right. (00:08:20)
Continuity mistake: When two divers emerge from the water, one pulls their goggles up onto their forehead and the other pulls his goggles down to round his neck. Then the divers and Mike start talking about 'no overtime', and between shots the goggles around the divers neck vanish. (00:07:30)
Factual error: When the shark swims towards the glass, it doesn't move its tail. Sharks have to swing their tail in order to swim. There is no way this shark could be moving.
Factual error: The window in the underwater control room has to be made from some thick material such as plexiglas to stand the pressure. Yet the shark simply lifts its snout a little and sends thin pieces of glass shattering everywhere.
Factual error: When the shark is chasing Mike and his girlfriend near the end you can see air bubbles coming out of the fin (obviously a hole in the puppet). Real sharks do not blow bubbles from their fins.
Factual error: At the end of the movie, the shark broke through the glass. When the entire room was flooded, the shark grabbed someone and started chewing them. Sharks don't chew their food. If their prey is too large to swallow whole, they rip it apart into smaller pieces.
Factual error: In the scene where they try to lure the shark, it eats that man. How is it possible to fit in a shark's mouth when only someone's leg did before? Also, if you look outside the shark's mouth, it isn't going anywhere, which is also impossible.
Factual error: The scene where the Shark is in the water/air circulation pump it swims backwards out of it. There is no way a shark could do that, it would drown.
Other mistake: When Jaws breaks the glass in the control room, it shatters and flies everywhere, but the water doesn't even move or give any indication of flooding the compartment.