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. (01:44:40)
Continuity mistake: After the cleats are ripped off, the size, shape and characteristics of the exposed area of wood underneath significantly changes in some of the following shots. (01:44:50)
Continuity mistake: Just as the first cleat flies off the stern of Orca, the shape of the small metal hood differs and the entire wood rail at the top of the transom in this close-up differs from the rail in all other shots. The long wood rail has another small piece of wood attached at the end, forming an 'L' shape with a 90° angle, whereas in all other shots the rail is one long solitary piece. (01:44:55)
Visible crew/equipment: In the scene after the shark has pulled out the stern cleats and the three men are kneeling down in the boat; look at the window of the cabin door of the Orca, and you can see the crew on a separate boat being reflected in the glass. (01:45:10)
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)
Continuity mistake: When the pump is given to Brody, Quint says, "Pump it out, Chief," and then Quint, with his long blue sleeves, thrusts his machete into the side of the boat. However, in the close-up Quint's arm has no sleeve whatsoever, as the machete meets the wood. (01:45:30)
Continuity mistake: While Quint leads the shark into the shallows, Brody asks, "Have you ever had a Great White do this?" and Hooper is beside the foremast holding one of the rungs, directly under the crow's nest. However, in the next shot, he stands at the edge of the bridge deck, beside the rigging. (01:47:25)
Revealing mistake: When Quint has decided to lead the shark back toward shore, after Quint pushes Hooper away when he tells him to shut up, Hooper tells Brody to hold on. In the next shot showing the three men, with the barrels in pursuit behind them, Quint moves toward the left of the screen and the line pulling the three barrels is clearly seen in the boat's wake behind it. (01:48:00)
Continuity mistake: Hooper runs into the very thick black-smoke filled cabin to go below deck, but in the next interior shot the entire cabin is bright and there is hardly any smoke anywhere. (01:48:40)
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 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. (01:49:05)
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)
Continuity mistake: During the shark's attack on Orca, the tall, large steam pipe clamped to the wall, beside the bridge deck ladder, actually differs from the steam pipe seen in previous shots. (01:49:55)
Visible crew/equipment: After Quint walks on deck and tosses the life vests to Hooper and Brody, Quint asks, "Hooper, what exactly can you do with these things of yours?" Just as Hooper turns around, the clear moving reflection of a boom mic and pole are visible on the glass of the door to the cabin, just behind him. (01:50:15)
Continuity mistake: As Hooper climbs into the cage, in the wideshot the regulator hangs down in front of him. However, in the next overhead shot the hose lies across his chest, with the regulator thrown over his shoulder. (01:51:45)
Continuity mistake: After Hooper enters the shark cage, Brody takes Hooper's eyeglasses and places the left earpiece in his mouth, but when Hooper tells them to try and keep the shark off him till he's lowered, it's the right earpiece that's in Brody's mouth. (01:52:20)
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. (01:52:40)
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)
Visible crew/equipment: When Hooper is underwater in the cage wearing scuba gear, very bright light reflections from the crew are visible on the regulator. (01:53:05)
Continuity mistake: Throughout the film, Hooper wears on his left ring finger a gold ring with a distinctive design and a small black stone. When Hooper is lowered in the shark cage, underwater the ring design differs and the stone is a much larger oval shape. (01:53:05)
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.