Continuity mistake: At the beginning of the film when the shark attacks the divers, you see in one shot that the shark already had a burned scarred face. The shark doesn't get set alight until later in in the film. This scene was one of the last ones to be filmed.
Suggested correction: The burned and scarred shark face is from the explosion at the beginning of the movie when the water skier's boat exploded.
This correction's false - the attack on the water skier's boat occurred well after the opening attack on the divers.
Continuity mistake: In the scene where Chief Brody comes home drunk, Deputy Hendricks comes over to express his sorrows. When he's leaving/already left, Both Ellen & Chief Brody comment on Hendricks as "Poor Jeff." In the first Jaws film, Brody calls him Lenny. Jeff is actually the first name of the actor who played Hendricks.
Suggested correction: It was a retcon from the filmmakers. Originally his name was Lenny, and then they changed it to Jeff. Same thing with The Mayor's children in the first movie. In the sequel, he only has one son; Larry Jr.
Not really a retcon, simply a mistake. Not every change, intentional or not, can be hand-waved away as a retcon.
The correction is valid. The person who submitted the mistake didn't watch the scene. They never said "poor Jeff", it was "poor Hendricks." But both Martin and Ellen call him "Jeff" in the scene and his name is said 3 times. Plus, if you read over the original script, the name "Jeff Hendricks" is mentioned 4 times.