Continuity mistake: On the Orca, after Brody's first attempt at a sheepshank, his hands grip the rope a couple of feet apart from one another. Between shots, his hands instantly come back together. (01:14:25)
Continuity mistake: When Quint slowly clips his harness to the fishing reel, the reel has a brushed chrome dull finish. However, in the previous and following shots, although the reel style is the same, the reel has a highly polished mirrored chrome finish. (01:15:25)
Continuity mistake: When the fishing reel clicks, Quint readies himself in his chair and Brody is finally successful with the knot. The knot in the rope, and the way he holds it, differs between the close-up and wideshot. (01:15:50)
Continuity mistake: Orca's ID number normally reads MS 15 LF on both her port and starboard side at the bow. However, after Quint shouts, "Hooper, you idiot. Ain't you watchin it?" Orca's ID number reads M 15 L at starboard side and 15 LF at port. (01:16:30)
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: The cleats are entirely different in many shots; they keeps changing from flat top, long, shiny silver with a wide base, to curved top, dull silver with a narrow base. When Brody unties the wrong line and when he wets the fishing reel it is the shiny flat top cleat on the transom. Yet, when he and Hooper tie off the lines the cleats are curved top. Also, the two metal plates and two metal hoods that are near the cleats repeatedly change from being very rusty, to not rusty at all. (01:17:40 - 01:22:00)
Continuity mistake: Just as Quint shouts, "You may be a big yahoo in the lab, but out here you're just supercargo..." and when he asks Brody to unbuckle him, the cleat at the stern has plenty of line wound round it and there is a red cup beside it. However, in the previous and following consecutive shots within this scene, there is no line and no cup. (01:17:50)
Continuity mistake: The fire extinguisher in the cabin, between the door and window, changes from an older tank to a clean newer one. Note the label and condition of red tank when Hooper sticks his tongue out at Quint and later when Quint removes it to put out the fire in the engine room. The silver clasp holding the tank reverses itself and the black holder changes its position on the wall between shots as well. (01:19:30 - 01:48:00)
Continuity mistake: While Brody and Quint are talking in the cabin, just after Hooper sticks his tongue out at Quint, the books on the shelf are fallen over on their sides. However, in the next shot when Quint walks out on deck, the books are visible behind him and now they're upright. (01:19:45)
Continuity mistake: When Brody starts chumming, the stern of the Orca is bloody and the white container is dirty and bloody. When he and Quint watch the shark coming towards them, the container is much cleaner and the pattern of blood on the boat, at the stern, differs. (01:20:45)
Continuity mistake: While Brody starts to chum, Quint goes to the cabin to sit and work on the fishing reel, and the portable stove is visible to his right. Then when Quint speaks with Amity Point light station the pots, kettle, etc., on the stovetop are positioned differently and now there is an additional white pot. The hanging net has fewer things too. (01:20:50)
Continuity mistake: Chief Brody has a cigarette dangling from his lips as he famously tells Quint, "You're gonna need a bigger boat." In the overhead shot as the shark passes the stern, just below Quint, Brody flicks his cigarette towards the left of the screen. However, when Hooper leaps down the ladder Brody's cigarette is back in his mouth. (01:21:20)
Continuity mistake: After Brody says, "You're gonna need a bigger boat." he and Quint go out on deck and there is a long rope tying the open cabin door to the rigging at the rail. However, when Hooper jumps down from the bridge deck the rope is gone. (01:21:25)
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: After Quint states that it's a 25-footer, he rushes below deck and when he comes up with the harpoon case, the gauges on the panel to his left are visible. When he answers the call from Amity Point light station, there is a new large black knob attached the corner of the panel, that was not there before. The paper mess at the top of the panel differs as well. (01:22:25)
Continuity mistake: As Quint lies to Ellen Brody on the radio and yammers that they caught a couple of stripers, the window above the portable stove in the cabin is spotless. However, a moment later when Hooper is on his way to get to the homing device, there is an interior view as he walks along the side of the boat outside. In this shot there are scraped blotchy remnants of a large rectangle sticker on that same window, above the stove. (01:23:15)
Continuity mistake: When Hooper runs below deck to get the homing device, life jackets hang on top of the rope, to the left of the machete. When Quint gets the machete there are no life jackets near it and when the engine hatch blows up, life jackets hang against the wall where the machete was. The life jackets near the fire extinguishers change position as well. (01:23:55 - 01:44:45)
Continuity mistake: When Hooper runs below deck to get the electronic homing device, in the wideshot he breaks apart the plastic case, throwing the clear top to one side and the yellow bottom to the other side. However in the next close-up the plastic case is suddenly intact, right below Hooper's hands. The yellow cord is in Hooper's hand in the wideshots, but not in the close-up. (01:23:55)
Continuity mistake: When Quint shouts for Hooper to tie up the first barrel, Hooper's grip on the electronic tracking device differs from one shot to the next. (01:24:15)
Continuity mistake: At Orca's bow, the hole in the steel hull beside its number, is oval shape. However, after Quint is gone, when the ship begins to sink, and later when Hooper surfaces beside the wreckage of the bow, the shape of the hole in the steel hull is completely different! The white water stain lines change throughout the shots as well. (01:25:00 - 02:01:10)
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.