Continuity mistake: When the divers are snorkelling underwater for lobsters, the diver in the blue swimsuit's snorkel keeps switching which side of his face it is strapped to. (01:03:40)
Continuity mistake: When Mike and Andy are on the sail-boat, adjusting the green sail, the zipper on Mike's blue lifevest alternates from being at the bottom / top of the zip on his vest. (01:00:20)
Continuity mistake: When the divers are positioning the cord on the rocks, in the opening shots, in one shot there is a tall seaweed plant, fully erect, floating around. In the next shot the plant is down in half, positioned totally different. (00:01:15)
Continuity mistake: When Brody sits on the beach, he begins to untie his shoelace of his left boot. In the next shot both of his boots are now magically off, and he is now pulling off his left sock. (00:34:20)
Continuity mistake: Brodie is racing in his vehicle down the beach to investigate an incident, driving to our left. He then gets out of the car and is shown running down the beach to the left. Unfortunately, the scene was shot with Brodie running to the right. The editor simply reversed the film so Brodie would be running the right direction. You can see backwards writing for about 2 seconds.
Continuity mistake: When Terry is water-skiing, the sky keeps alternating from cloudy to sunny and back, and the roughness of the waters she skies on changes as well. (00:17:45)
Continuity mistake: After Chief Brody is fired from his job, he comes home drunk. No beer cans can be seen spilling out of his car or on the ground. The next day when he is taking his wife to work, there are several empty beer cans on the ground. Where'd they come from?
Continuity mistake: Chief Brody and his raft disappear from under the shark when it catches fire. Understandable, as they were burning the model shark for real, but still poorly edited.
Revealing mistake: In the overhead shot, when the shark is going under the "Tina's Joy" boat, you can see the shark is being driven by a propeller as the water behind it foams. (01:11:20)
Continuity mistake: When Dr. Lureen Elkins is walking around the dead whale you can see a man in a black t-shirt in the background covering his nose with his hand and then lowering his hand. When it cuts to a close-up of Elkins and Brody, the man is still covering his nose. (00:27:40)
Continuity mistake: The boat Tina's Joy is hit on the sideboard by the shark and a portion splits off. When they are rescued the boat is intact.
Continuity mistake: Brody fires six shots from his revolver after coming down from the tower. He ejects the shells on the beach. Then he squats to pick them up and there are many more than six.
Continuity mistake: When the young guy is fiercely swimming back to the sailboat, the shark yanks him under a few times as he struggles to climb back in the boat. Suddenly there is a huge pool of gushing fake blood floating all around before he's even pulled back under.
Factual error: Several times Chief Brody was seen to both transmit and hear the boat radio without him taking his finger off the mic button. If the button is pressed you can transmit, but not receive.
Continuity mistake: While the shark pulls the police boat the sun changes between shots.
Continuity mistake: While the shark attacks the waterski boat the sun changes between shots.
Revealing mistake: When Chief Brody sees the driftwood in the water, he sits down and takes his shoes off to wade in. As he sits down, his butt is already wet, even though he sits in dry sand.
Factual error: Brody would have also received a shock inside his raft due to proximity and water continuity.
Continuity mistake: In the beginning of the movie when Terry is water skiing, the boat has a 70hp 3 cylinder Johnson. When the shark is eating the boat it's a 1977 55 horsepower motor that still has the 70hp decal on it.
Other mistake: When the shark grabs and eats Marge, there is no blood at all.
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.