Revealing mistake: When the shark bursts through the window of the cabin, in each of the shots facing Brody, including when he shoves the air tank into the shark's mouth, the glistening water is visible in the window's reflection behind Brody. The shark's reflection is never seen behind Brody, despite the shark's massive size in the small cabin. Bruce must have had the day off during Roy Scheider's takes.
Continuity mistake: When Hooper gets his gear from below, after the explosion in the engine room, he runs to the deck passing Quint using the fire extinguisher. The camera pans from Brody, who stands on the bridge deck, to Hooper right below him. So where exactly is the tall iron ladder that leads up to the bridge deck in this shot? It should be behind Hooper, in front of the window, but it's gone. Don't fret, it's back in the following shots.
Visible crew/equipment: When the fishermen start out on the hunt, Ben Gardner appears in a close-up leaning on the windshield at forward deck, while talking about how stupid some of the others are. In the next wide shot of the boats, Ben's green boat is towards the left of the screen, and the large reflector screen and camera, that are mounted to the bow of his boat, are visible in front of the forward window where Ben is seen in the previous shot.
Continuity mistake: At the scene just after the fake shark scare, the real shark shows up at the pond area of the beach. As the lifeguard in a small boat reacts to everyone's panic, the shark tips over the boat then appears underneath him to tear his leg off. We watch as it sinks slowly to the bottom. You can plainly see that the lifeguard is barefoot in the boat. The severed leg has a tennis shoe on.
Continuity mistake: Quint embeds his machete into the wood at the side of the boat, but in the following wideshot the machete is gone. Then as Orca starts to move, when Hooper says, "He's chasing us, I don't believe it," the machete is back. But when the shark leaps onto the boat the machete is gone again, and then as the shark devours Quint the machete is back for him to grab, so he can valiantly stab the shark.
Revealing mistake: In the scene in which the two men are fishing for the shark with the roast and inner tube, watch the amount of chain that is pulled off of the pier. Not only do numerous feet of chain go out but there are already many feet in the water connected to the tube. When the pier gets pulled into the water and the shark makes the turn to chase after Charlie, watch how close the pier is to him. With the amount of chain that was let out, the shark would have been well past Charlie and the shark probably would've beached itself.
Continuity mistake: When Chief Brody is standing on the boat, almost ankle deep in water, he throws down the pump and is about to climb up the ladder. In the next shot, while he is on the ladder, the shark (we presume) hits the boat making it list to the right and the deck is dry.
Continuity mistake: The number of barrels on the deck of the Orca changes from shot to shot, during the final scenes at sea.
Continuity mistake: When the shark bursts into Orca's cabin and tries to attack Brody, in the shots facing the shark, at the right of the screen is the forward window. The previously shattered glass (from the yellow barrel) is now perfectly intact within the window frame, and the large wood cabinet below that window is gone. The glass is shattered once again, when Brody climbs out of the cabin, through the window beside it.
Character mistake: On the death certificate for Chrissie, the shark's first victim, the date of death is July 1st. But later, on the reward paper posted by the boy's mother, it says that the date of Alex's death was June 29th. Alex died after Chrissie, not before. Also, the form refers to the coroner as the "corner."
Revealing mistake: Just as Quint finishes scraping his nails on the chalkboard, the camera begins to move in closer when he takes the first bite of the cracker. On the right side of the screen under Harry's chin, Roy Scheider is seen ducking down while staring at the camera, as it pans toward Robert Shaw, and he then lifts his left hand up, cueing Robert's line.
Continuity mistake: Before Alex's attack, the guy who plays with his dog Pippet on the beach wears a bright yellow Izod polo shirt with straight hemmed sleeves, in all of his close-ups. However, in all of the wideshots the polo he wears is pale yellow, with shorter sleeves that have the classic rib-knit sleeve openings.
Revealing mistake: When Quint is gone, the shark bursts through the window of the cabin surprising Brody and in its second close-up, with its jaws wide open, the shark's head moves from left to right of the screen. As it does, the aft side of the cabin set is visible on the left, with the wall conspicuously missing and then at the fore side of the cabin, the window frame is not complete.
Visible crew/equipment: After Brody buys the sign supplies, when Hendricks shows up Brody places the box in the front seat, and as Hendricks tells Brody about the Boy Scouts, pay attention to the left window across the street, where we can see one of the local residents holding a camera and looking out the window facing the location shoot, taking pictures of the actors and film crew.
Continuity mistake: When Quint goes below deck to get the machete, with the intent to cut the barrel lines, the machete he takes is shiny and clean, with no rust or pit marks at all. Yet, when Quint holds it over his head and then embeds it into the side of the boat, the entire blade is rusty and full of pit marks.
Factual error: When Hooper sees the hole in the hull of Ben Gardner's boat, he uses his knife to pry out the shark tooth. The tooth is located at the bottom of the hole, with its flat root side stuck deep in the wood and its pointy side facing up. It is completely impossible for the shark's tooth to become wedged in the wood this way, while he takes a nice bite out of the wood hull.
Continuity mistake: At the harbor, just as Brody asks, "Help me get those guys out of the boat, will you?" in the wideshot there are five men standing on the dock and three standing in the boat. Then in the next close-up, there are four on the dock and four in the boat. The one in a black/white check shirt is now at the end of the dock and the one in a black rain slicker, that was standing on the dock, is now suddenly standing in the boat below, at its stern.
Continuity mistake: Quint slams the machete into the wood beside the side cleat, and rigging lines. However, when the shark joins them aboard the boat and Quint is sliding towards its mouth, the machete's position changes - it is farther down towards the stern, note the black anti-slip mats.
Revealing mistake: When the shark takes the fishermen's bait, the attached chain pulls one corner piling at the corner of the small dock. When the dock gives way in the wide shot, another line around the second corner piling visibly pulls it as well, in order for the dock to break apart effectively for the stunt.
Continuity mistake: When Brody and Hooper first arrive at Quint's place, Quint goes to pour the drinks, and beside him are windows with shades. There is a fish that hangs over the window beside Brody and the window upstairs, above Quint, is open. In the following shots positions of the roll shades, towels, etc., differ. Then when Quint climbs the ladder a bunch of rope now hangs beside the mirror, there is a small net that hangs with the fish above the window, and the window upstairs is now closed.
Continuity mistake: There is a scene where Chief Brody and his wife are talking about their son's birthday present. She says that he probably won't go in the water after what happened yesterday (the attack on the Kintner boy). The next day is when the shark is caught and Hooper makes a comment about the shark's digestive system being very slow and anything he's eaten within the last 24 hours would probably still be in there. From the earlier scene it would make it 48 hours since the Kintner boy was killed.
Continuity mistake: When Hooper climbs into the cage he is not wearing fins, yet when he is lowered in the cage, in the very first shot underwater, he is wearing fins. In the following shots he is not wearing fins, but after the shark destroys the cage and he swims to the bottom of the ocean, he is wearing fins once again.