Factual error: When the woman is yelling that the shark is in the pond, it shows the shark's dorsal fin and tail fin sticking out of the water. The tail fin is moving straight. If the shark needs its tail to swim, wouldn't the tail fin be moving side to side? (01:01:00)
Continuity mistake: On the Fourth of July, Sean (the youngest Brody kid) is wearing a white t-shirt with orange around the collar, and green shorts. But after Michael goes into shock and Sean is seen crying, he's suddenly wearing darker shorts and a plain white shirt with no orange. Later at the hospital, he has his orange and white shirt and green shorts on again. (01:01:55)
Continuity mistake: When the shark enters the Estuary, he passes Sean playing on the sand. After the attack Michael is pulled ashore and there is a close-up of Sean crying. Behind Sean the orange and white stripe cabanas are visible. However, there are no cabanas at the shores of the pond; these cabanas are located at the main beach area. The footage of Sean, with the cabanas behind him, is from the earlier scene of Alex's attack. (01:02:00 - 01:03:30)
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: 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. (01:02:15)
Continuity mistake: When Brody helps the boys pull Michael out of the water his uniform is soaked - much, much wetter than it should have been. In the next shot only the bottom of his pant legs are wet, and in the following shot the wetness of his uniform differs again. (01:03:20)
Continuity mistake: At the hospital, when Ellen walks away carrying Sean, Brody turns to face the Mayor and the countertop of the nurses' station is visible. In the next shot, a black ashtray suddenly appears on the counter as Brody walks over. (01:04:45)
Continuity mistake: At the hospital, where Larry waits for Brody to approach, Larry quickly moves his left hand away from the front desk between frames. (01:04:50)
Continuity mistake: In the scene where the shark eats the guy in the red boat in the pond, Brody grabs a red blanket and goes for a brown blanket after exclaiming, "He's in shock," in reference to his son's close encounter with the shark. In the next shot, his wife is laying down blue and brown blankets over Michael. (01:06:05)
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. (01:06:15)
Continuity mistake: While Brody and Hooper are at Quint's, just as Quint says, "And don't forget the color TV," the six small shark jaws hanging on the far wall, beside the window to Brody's left, are visible. However, when Hooper ties the sheepshank knot, there are only three small shark jaws beside that same window, near the stove. (01:06:30)
Continuity mistake: At Quint's place, he lifts two shark jaws out of the boiling water on the stove, in the close-up. In the next wideshot, the two jaws are positioned differently within the tongs Quint holds. (01:06:55)
Continuity mistake: At Quint's, when he holds the two steaming shark jaws, assorted dry goods on the shelves above the stove are seen, particularly the cans of Del Monte vegetables. When Quint gives Hooper the rope to tie the knot, some of the goods on the bottom shelf and every can of veggies on the top shelf are entirely different. (01:07:00)
Continuity mistake: When Quint stands beside the stove at his place, the stove is positioned a particular way in front of the wall. When he gives Hooper the rope, the stove is farther down against the wall and the wall behind the stove differs (note the panels), as do the roll shades on these windows. (01:07:00)
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)
Other mistake: The five yellow barrels are not on the Orca when they are getting ready to leave shore. When Quint begins singing, goes and stands at the cabin door, you can see through the front windows that the barrels are not there. With the Orca leaving just moments later, they should have already had the barrels on board. (01:07:30)
Continuity mistake: Prior to departing on the Orca, Hooper and Quint discuss the anti-shark cage. At the onset, a rigging rests on Quint's left shoulder. But between shots the rigging repositions itself away from his shoulder. (01:09:50)
Continuity mistake: When Brody boards the Orca, as Quint shouts, "Daylights wasting," the other docked boats along the surrounding shoreline are visible; for example, right across the docked Orca is a yellow boat pinning a white boat between it and the shore. When Orca gets underway, the yellow boat now pins a red boat between it and the shore, and in the close-up of Brody at the stern, there is a small white boat to his left that disappears in the next wideshot. (01:11:40)
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: When Brody is throwing chum in water and Quint is in the chair they show him wearing no socks and old tennis shoes. After Brody falls and then sets a new chum marker Quint has brown socks on and loafer type shoes. (01:12:45 - 01:14:00)
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.