Revealing mistake: As Quint smashes the radio, then when Brody yells at him, nearby land is reflected in the windows behind them. There is no land in sight both before and after this scene.
Continuity mistake: When Brody is on the mast of the Orca with Quint's rifle, preparing to shoot the shark, the shark emerges from the water and there is blood on the end of its nose, but after a quick cut to Brody, we return to the shark and blood has disappeared. (01:59:20)
Continuity mistake: When the shark is attacking Hooper in the cage, what happened to the the lines to the barrels they have shot into the shark?
Continuity mistake: When Hooper is lowered in the cage, Jaws approaches with the barrels attached, but when he passes the barrels are gone and never return.
Continuity mistake: When jaws jumps on the back of the boat, Quint falls on the floor and the shark's head is 3/4 submerged - in the next shot the head is fully above the water and submerges again.
Continuity mistake: When the guy is standing on the beach in the opening scenes the sunset is covered by cloud. When seeing the sunset from the woman in the sea's perspective the sky is clear with no clouds. (00:02:50)
Continuity mistake: The seat that Quint sits in with the fishing reel disappears after that scene has finished. These seats are bolted to the deck. (01:25:50 - 01:35:25)
Continuity mistake: When Jaws gets trapped between the cage and the boat the shark is really thrashing about. Cut to the surface and Brody is trying to free the cage - the surface of the water does not match the actions of the shark.
Continuity mistake: When Quint drinks the beer then crushes the can, the sea behind him is all choppy. When Hooper crushes the plastic cup, the sea behind him is virtually calm. (01:13:15)
Continuity mistake: When Hooper cuts open the shark and empties the contents, the amount and position of the fish changes between shots. (00:44:00)
Revealing mistake: When Quint is getting eaten, the Orca is now a solid tilted movie set - look at the sides against the sea instead of Quint, and the Orca is not moving.
Continuity mistake: When they are chasing down Jaws with the first barrel on, look at the sea. It's calm at the front of the boat and rough behind when we see close ups of Hooper.
Continuity mistake: When Hooper is lowered in the shark cage, his right hand holds a dart while the left holds a cage bar. But as soon as the angle changes, Hooper's dart changes hands as well. (01:52:55)
Continuity mistake: Throughout Quint's speech in council chambers, the door behind Brody continually opens and closes in alternating shots. (00:21:25)
Continuity mistake: As the townspeople make their way into council chambers, we can see Mrs. Taft talking to Chief Brody before she takes a seat. Between frames, her purse strap removes itself from her left shoulder. (00:19:00)
Continuity mistake: As Brody sits on the shore with Ellen, a councilman approaches. Between shots, Brody's left hand changes position - jumping from his lap to the back of the beach chair in an instant. (00:15:15)
Continuity mistake: When Brody questions Tom about Chrissie's disappearance, Brody turns his head away from Tom between frames, just as they hear Hendricks' whistle. (00:08:00)
Continuity mistake: Before Quint meets his fate, we see him lose grip with Brody's arm. But in the following shot Quint is still holding onto Brody's arm despite having let go just a moment ago. (01:57:05)
Continuity mistake: When the shark rams Hooper's cage, Hooper loses the spear and when it is shown floating through the water, it hits the sea floor just before it cuts to the live shark footage. Following the live shark footage, the spear is shown hitting the sea floor again. (01:49:45)
Revealing mistake: On the second day aboard the Orca, Quint fires a barrel into the shark and they start to pursue it. There are some overhead shots of Quint on the pulpit and during some of these shots, you can see some sort of tow cable. It's visible on the bottom of the screen between some of the supports of the pulpit.
Chosen answer: As mentioned in the movie, the posion was in the needle and the shark's hide was too tough for the needle to penetrate. Hooper had to go in the water so that he could get the needle into the shark's mouth, where the flesh was less tough.
Kevin Howard