Continuity mistake: While Quint slides towards the shark and subsequently munches on him, then leaves, the articles and debris on the deck noticeably change between shots, regardless of the water splashing about. (01:57:05)
Continuity mistake: As the Mayor walks over to the couple on the beach, to persuade them to go into the water, the back of the woman's lounge chair is visible. In the following shot from behind, as they stand up, suddenly a yellow towel is leaning over the back of her chair. (00:56:05)
Continuity mistake: After Brody says, "You're gonna need a bigger boat," he and Quint step out on deck and stare beyond the port side. However, in the next shot from behind them, they face starboard side as the shark swims nearer, but when Quint says, "Shut off that engine," they face port side again, with a close-up of Hooper looking port side as well. Then finally Quint follows as the shark passes from starboard to port side. (01:21:30)
Continuity mistake: When Sean mimics his father, Brody's glasses are lying upright on the table. However, when Hooper sits down the glasses are upside down and other things on the table change position, etc. (00:38:10 - 00:39:50)
Continuity mistake: While Quint makes his offer at the town meeting, when he says, "I don't want no volunteers, no mates...," the chalkboard is beside him in this close-up. The doodle of the shark on the board, and the actual wood grain of the chalkboard frame all differ from the previous shots. (00:21:40)
Continuity mistake: When Michael and his two friends are sitting in their boat, in the pond, in the first close-up they sit on the white wrinkled up sail, but in the next wideshot two of them sit on the spread out blue tarp. (01:02:00)
Continuity mistake: As Quint and Hooper drink to their legs, Brody lifts his sweater to see his own scar. Beside the portable stove, to Brody's left, there are four canned goods behind the green canisters of gas. Just after the shark starts to ram into the boat, there is a close-up of the stove, but now there are only two canned goods, a cup appears, and other changes in position, eg the liquor. (01:28:20)
Continuity mistake: While Hooper and Brody speak with Quint at his place, Quint tosses a large duffel at Hooper. In the shot looking up, the opening of the bag faces Quint, when it is inches away from Hooper's hands. However, in the next overhead shot as Hooper catches it, the duffel now faces the opposite direction. (01:07:25)
Continuity mistake: As Orca heads out, first there is an interior shot that pans in through the large shark jaw framed window, showing the Orca a good distance away from Quint's place. However, in the next close-up of Brody, the Orca is just pulling away from shore. (01:11:55)
Continuity mistake: After Hooper says, "Oh boys, I think he's come back for his noon feeding," when Quint rushes to the pulpit one of the iron rail bars around the pulpit is bent, but in the following shots it is straight again. (01:39:15)
Continuity mistake: After Quint scrapes the chalkboard with his nails, in a close-up when he says, "Gonna stay alive and ante up, or gonna play it cheap," the papers pinned to the bulletin board are visible in the room behind him, as well as the chair, etc. In Quint's next close-up, the papers differ with additional pink and blue sheets and the chair is now at the other end of the board. (00:21:20)
Continuity mistake: In the council chambers, after the Mayor says, "Only 24 hrs," as the people argue in the wideshot a particular area of the chalkboard is visible behind them and it is blank. In the very next close-up Quint, who was not in the previous shot, scrapes the board with his nails, which now shows the large doodle of the shark, that should have also been visible in the previous shot, but was not. (00:20:30)
Continuity mistake: When Hooper and Brody tie off the stern cleats, the amount of line, and the way the lines are wound round the cleats, varies in the following shots. (01:42:35)
Continuity mistake: In his bedroom, when Chief Brody asks, "How come the sun didn't used to shine in here?" the ashtray and lamp are visible beside Ellen. In the following shots the ashtray and lamp's electrical cord noticeably keep changing positions. When he walks out of the bedroom, something (mug?) appears on the desk near the window that wasn't there in the previous shot. (00:05:20)
Continuity mistake: At the end when Brody is up in the crow's nest of the Orca waiting for Bruce to get close enough for him to shoot the tank in Bruce's mouth, notice that the crow's nest is sinking much faster than Bruce is moving towards him. At these rates, the boat would have fully sunken before the shark got close enough.
Continuity mistake: While Brody is in the flooded cabin, before the shark joins him, in the shots facing the aft cabin wall a few things are very different. The wood paneling on the entire wall, the porthole window beside the door, the ceiling and the black fire extinguisher holder all differ, and the round fixture that was screwed into the wall is gone. Also, visible through the window, the permanent ladder is positioned differently and things hanging in front of the window differ from the previous shot. (01:49:00 - 01:57:40)
Continuity mistake: When Quint shouts for Hooper and Brody to get their gloves on, in the wideshot Hooper starts to slip his left hand into his left glove. However, in the close-up, he just starts to put his right hand into the right glove. (01:17:40)
Continuity mistake: When Quint is wearing the bandana round his head, the design showing and thickness of the bandana keeps changing in consecutive shots. (01:36:50)
Continuity mistake: After the two barrels are tied off, there is at least twenty feet of line between the barrels and where it disappears into the water. When the next harpoon is shot (the barrel shatters the cabin window) and the shark pulls Orca, that last barrel trails way ahead of Orca, its taught line being extremely shorter than the lines leading to the two other barrels, though the shark pulls them at the same time. However, once the cleats break off, the length of the three lines are identical in length. (01:44:15)
Continuity mistake: When Hooper removes the pump from the locker, in the close-up Quint takes the pump with his empty hands and gives it to Brody with both hands. However, in the wideshot he is holding the machete in his left hand, as he gives Brody the pump. (01:45:30)
Answer: Possibly a scar from having his appendix removed, I've been told.
The appendix shot is Brody - he is feeling inferior as the other two share tales of the sea and the only scar he has is from his appendix being removed.