Revealing mistake: Just after the first shark attack, Chief Brody and his deputy discover the beached remains of the nude swimmer. As Chief Brody hesitantly approaches the grisly scene, the camera cuts to a close-up of a mutilated female arm and other viscera, covered with a creeping cluster of small saltwater crabs. Inexplicably, a single crab falls out of thin air on the right side of the screen to join the others. A moment later, Chief Brody arrives at the scene, in the background. Obviously, a film crew member dumped a bucket of live crabs onto the body parts for this shot, but poor editing allowed one of the animals to be seen falling onto the pile.
Continuity mistake: At the end Brody throws the diving tank into the shark's mouth with the bottom first. When he shoots the tank it has turned round with the fat end facing out.
Other mistake: The five yellow barrels are not on the Orca when they are getting ready to leave shore. When Quint begins singing, goes and stands at the cabin door, you can see through the front windows that the barrels are not there. With the Orca leaving just moments later, they should have already had the barrels on board. (01:07:30)
Continuity mistake: Before Alex Kintner is attacked, Sean Brody is shown sitting on the beach singing. After Alex is attacked and people are running out of the water, Sean can be seen standing on the beach, and in one shot, Chief Brody can be seen grabbing him. But a couple of seconds later, Sean is shown sitting on the beach in the same spot he was before, as if he hadn't moved. (00:16:55)
Character mistake: When Hopper is in the cage you can tell it isn't him by the size of the scuba tank on his back and size of that kill stick he was going to use. The tank and kill stick are almost as tall as the person in the cage. When on deck and loading into cage in scene before that the items aren't that tall.
Other mistake: Two errors when Hooper is at the helm...the first is Quint yelling at Hooper "starboard, ain't you watching?"the shark is actually running from the port side of Orca. The second is when Quintbtells Hooper to head SSE...Orca turns to starboard while moving ahead...a SSE course would be a turn to port.
Continuity mistake: When Jaws leaves the pond after the attack its fins go below the water as it approaches the bridge, the scene immediately changes to the bridge, the woman is shouting "shark" and we see the fins go below the water again.
Continuity mistake: When the man gets attacked the long shot shows two of the three boys on top of the upturned boat, then we see the leg sink to the bottom with a trainer on, even though the man was bare footed. Then the camera passes the boy in the water and the other two boys are only just climbing up onto the boat.
Revealing mistake: Towards the end, before Quinn is eaten, the shark is "chasing" the boat with 2 barrels. You can see the wire from the boat dragging the barrels off to the right side of the screen.