Continuity mistake: When they are all sitting at breakfast, Michael says how he's going out sailing. The position of the mini Rice Crispies box on the table turns about 90 degrees between camera shots.
Continuity mistake: Brody has a hold of the large power line, and the shark is gliding along straight for it. In all the shots of Brody holding the power line, the green jacket he wears has wet splashes on it. One patch of water on his right shoulder briefly disappears for one shot, the reappears in the following. (01:46:45)
Revealing mistake: When the shark attacks the catamaran remains which only Jackie and Sean are on, as the shark hits, one of it's front top teeth is clearly bent in half. It remains back to intact in all other following shots. (01:44:30)
Continuity mistake: When Eddie is floating the water, after being knocked out of the boat by the shark, in one shot we see his hair is totally soaked and is flat. But in the next shot it is drier and now curlier. (01:10:30)
Continuity mistake: When Andy and Mike are standing on the boat, the position of the boat's green sail changes from shot to shot. The two red stripes on the sail clearly verify this - watch them as they change position and location as well. (01:00:20)
Continuity mistake: When Andy and Mike are standing on the boat, adjusting the green sail, between shots the boats on the water behind them completely change. (01:00:20)
Continuity mistake: When Tina and Eddie stumble upon the huge dead whale on the beach, they are standing upon a large sand dune to the whale's left. However in the next scene where everyone is gathered around and Dr. Elkins measures the bites in the whale, the sand dune has mysteriously vanished. (00:27:00)
Continuity mistake: When Hendricks pulls the thick power line out of the water, the position of the seaweed and plant life hanging from the line changes and decreases depending on the shot. Also, the way in which the white claws are inserted into the power line change too. (00:24:45)
Continuity mistake: When a group of teenagers are aboard a boat, hauling the boy back and forth on the bungee swing, between shots a bunch of boats and catamarans which are drifting on the water behind them, suddenly vanish. (00:16:35)
Continuity mistake: When a group of teenagers are aboard a boat, hauling the boy back and forth on the bungee swing, between shots the positions/locations of the teenagers changes. (00:16:00)
Revealing mistake: When the shark attacks the sailboats with only Jackie and Sean aboard at the end, you can see that it is a totally different mechanical shark right down to the bad paint job.
Character mistake: When Dr. Elkins is measuring the Killer Whale, she says "111 centimeters" followed immediately by "68" (centimeters). But her arm spread shown when she says that is not 111 centimeters - about 3.6 feet (1+ YARD wide). It's more like 2 feet. The "68 centimeters" is actually more accurate for the shot though: 26 inches, which is shown.
Other mistake: The dead Killer Whale washed up by the lighthouse was visible from the teens AND in their line of sight while they sat on the shipwrecked boat, also their Catamarans they pulled onto the sand were literally 100 feet away - as seen in the wide shot, but yet it was a surprise when Tina and Eddie come upon it. There's no wrack line showing in the sand so the whale didn't "just wash up "
Continuity mistake: When Brody is out looking for the teenagers on the police boat, he is shown approaching the lighthouse while passing a buoy on the left of screen. When we see Brody and the police boat from behind the top of the lighthouse, there is no buoy anywhere. (01:23:55)
Visible crew/equipment: On the morning after Brody is fired, when his wife gets up from the kitchen table and talks to their house keeper, the shadow of a crew member holding a boom mic can be seen on the wall on the right side of screen, while the shadow of the boom mic is visible above the doorway. (01:08:20)
Visible crew/equipment: When Brody is at the film developer's darkroom, the developer pulls a covering over what is supposed to be a skylight. Right before the covering is fully pulled over, the "skylight" starts to dim as if it was really a stagelight. (00:50:50)
Continuity mistake: When Brody walks out of the bathroom with a towel hanging over his left shoulder, he opens Mike's bedroom door. Between shots the position of the towel over Brody's shoulder changes, as you can tell by the designs on it. (01:06:45)
Continuity mistake: When Mike and all of his friends are at the bar, Mike has a glass of coke on top of a napkin, sitting in front of him. However in one shot of Mike saying “yeah, sure,” the coke has vanished. Through the same bar scene items on the bar change their positions, move around, appear, etc,. (00:53:40)
Continuity mistake: When the two guys are trying to pull Mike back onto their boat, in the first shot they are pulling the front of his jacket. Then when the shot changes, they are pulling him up by the back of his jacket.
Continuity mistake: When Ellen Brody is talking with the Mayor and Hendricks on the docks, about her husband, her collar goes from under to over her jacket between shots.
Answer: For what it's worth, in the novelization the shark is a female and pregnant with the offspring of the first movie's shark, but that's not brought up in the film at all.