Continuity mistake: The word ORCA on the back of the boat continually changes from shot to shot varying from very rusty letters to shiny letters.
Continuity mistake: Just before the Kintner boy is attacked, when Chief Brody is sitting on the beach watching the water, he speaks with the old man called Harry. In the close-up shot of Harry the chin strap of his rubber cap hangs down loose at his chest, but in the side shots the chin strap is tucked up at his ear (seen when Harry stands up). (00:16:00)
Continuity mistake: After the first barrel pops up, Hooper and Quint gather up the rope while at the stern. The existence of rope in each of their hands changes abruptly between shots. Particularly when Quint holds the rope only in his left hand in the wide shot, but in the next dramatic close-up as it leaves a rope burn, he grips it in both hands. (01:37:30)
Visible crew/equipment: While Quint tells of his experience with the U.S.S. Indianapolis, in the close-ups of Brody a crew member's arm with a watch is clearly visible moving in the reflection on the window, just behind Brody, particularly when Quint says, "Anyway, we delivered the bomb." (01:32:55)
Continuity mistake: When the shark slams into the cage and makes Hooper drop his weapon, it shows the underside of the shark; look at the its mouth. When the shark is about to slam into the cage again its mouth isn't the same size as it was before. You can tell that they used a real shark when they showed the underside. (01:54:15)
Revealing mistake: When Chief Brody starts shooting the shark, his cartridge is missing.
Character mistake: When Brody waves at his wife Ellen she says "I've got Shawn." In the next shot he's running after his brother Michael going to the pond, so she has not got him at all.
Revealing mistake: When Quint begins singing 'Ladies of Spain' while Bruce is chasing the Orca into the shallows, he turns slightly to his left and looks over his shoulder. When he does, you can see that the barrels are actually being towed by the Orca, due to the wake of the line doing the towing.
Revealing mistake: When the boy is attacked at the beach a man says "did you see that?" The woman behind him wearing the hat sits up with everyone else then looks directly at the camera and smiles instead of looking at the attack.
Character mistake: Captain Quint tells Hooper and Brody that the USS Indianapolis delivered "the Hiroshima bomb" in 1945. This is a myth that has persisted for decades and right up to the present. To prevent it from being lost in one piece, the Hiroshima bomb was actually delivered in pieces by various means to Tinian Island, where the parts were reassembled before it was carried aboard the Enola Gay to its target in Japan. The USS Indianapolis delivered only the detonator for the bomb. (01:29:00)