When Tina and Eddie discover the dead whale on the beach, they are standing on a large sand dune which is right beside the whale. When Chief Brody and Dr. Elkins arrive on the scene the sand dune is gone.
The shark in Jaws (1975) smashed through the port side of the Orca, but at the beginning of this film when the divers find the wreck of the Orca, the port side is untouched. There's a sign saying "Orca" under the pulpit of the boat which was not there in the original film. The only place where the name "Orca" appeared was at the back of the stern.
When Ellen Brody is hugging an hysterical Tina on board Tina's boat, she holds her arms in an embrace, before putting her hands around Tina's head. In the next shot she is seen again holding her arms in an embrace as if the second shot hadn't happened. The shot after this shows Ellen again holding Tina's head.
Near the end of the movie, there's a shot of the shark cruising past Sean and Jackie. In the background, Patrick and Lucy can be seen sitting on the rocks of cable junction. A few seconds later, they are seen being helped out of the water.
After Brody questions the old lady about the explosion, he turns and grasps the outside of the porch column. When it cuts to a close-up, his wrist is against the inside of the column.
Brody wears his badge on the right side of his chest, whereas all uniformed law enforcement officers wear their badges over the left.
When Chief Brody is extracting sodium cyanide, he is doing so by injecting dark-blue liquid. In reality, sodium cyanide is colorless and, at best, could be described as being a 'white/crystalline or granular powder'.
When the shark first attacks the kids, Jackie and Sean fall into the water, but in the next scene they look liked they never did.
However, the amount of time that passed between these two scenes is not known, and it could well be that they dried off in the hot sun.
When Brody fires six shots at what turns out to be bluefish during the crowded beach scene, he unloads the spent casings from his revolver as if he is going to reload. He doesn't reload, but he stoops down and picks up 9 casings off the sand. Upon closer examination, the unspent bullets can be seen on the sand with the empty casings. (Sean picks at least one up.)
It is likely that while Brody was struggling to reload with fresh bullets he had in his pocket, he dropped them onto the sand, at which time he was told that he was only firing at a school of bluefish.
The old lady is looking straight at the boat when it explodes, yet she fails to see the shark on fire next to it before it drops back underwater. Similarly, she hears the sound of the boat moving earlier, as does Tina, yet neither of them (or Eddie) hear the boat driver's screams or the sounds of the boat being destroyed by the shark. In actual fact, the old lady had a book in her hand when she first sees the waterskier's boat and no doubt got back to her book up until the boat exploded. Likewise, Tina was no longer in in sight of the boat once she returns to Eddie in the dunes. As for the sound of the shark attack, the shark itself does not make any noise and woman's screams would not necessarily have been as loud as the boat engine (even if they were, it could have been mistaken for the women having a good time rather than terror).
After the dive captain is injured, Hendricks tells Brody it happened before the kids went sailing to the lighthouse. Brody, Ellen and Hendricks rush to the police boat, and when Hendricks asks Brody where he wants to go, Brody says, "You said something about a lighthouse." Brody had been sheriff of Amity for four years, so he would have known about the lighthouse and where it was. However, there are likely more than one lighthouses in the area, depending upon how far the kids sailed.
When Brody sets out in the police boat to find the boys with his wife and the deputy, he has a green MA1 type bomber jacket on (which he left the house wearing). When they find the girl hiding in the drifting sailboat, he takes this jacket off and wraps it around the girl and hands her over to his wife. His wife, the girl and the deputy then wait for a nearby boat to take them back to land while Brody continues on by himself in the police boat looking for the other kids. He does not take his jacket with him and is seen only in his T-shirt and shorts. However, at the end of the film, Brody is wearing a green jacket again. However, this is an army type jacket that is a completely different style to the MA1 jacket, and has front breast pockets and epaulets (straps) on the shoulders which the MA1 jacket did not have. It is possible that this jacket was already on the police boat beforehand and Brody simply found it and put it on as the weather was changing.
When the kids are lifting the unconscious Mike Brody out of the water and the shark swims past the side of the boat, the main pneumatic piston in its mouth can be seen, and the mouth gets all bent out of shape when running alongside the boat.
In one of the sequences where the shark attacks the kids, underwater shots of the shark (meant to be a great white) actually are stock footage of a black tip shark. This is obvious from the black tip markings on the visible dorsal and pectoral fins. It is a smaller and less aggressive shark than the great white.
Near the end of the film, as Brody begins to climb out onto the power cable, it cuts to a shot of Andy and Larry, who swam to Cable Junction island, sitting on the rocks at the waters edge watching him. The entire set of "rocks" that they are sitting on are bobbing up and down in the water with them. This was due to the fact that the entire island was made from fiberglass and was build upon two large barges (see Trivia).
As Brody approaches Mike and his friends in the sailboat while searching for them, it's apparent that they are both sailing towards each other along a stretch of deserted beach from the wide shots. Also, in the wide shots, it's obvious that the weather is turning bad. However, in the closeup shots of the actors tying the boats together, not only is it now sunny and clear out, but there is suddenly a large bridge behind the three kids' boat that wasn't there a moment ago. Brody unties from the boat and the wide shot of him pulling away shows impending bad weather again, showing that the wide shits and the close-ups of the boats docking were not only shot at different times but also in different places.
When Brody leaves his police car and walks down to the beach to look for evidence, he looks into the water then sits on sand to remove his shoes. As he sits, the seat of his pants can be seen to already be soaked. The scene apparently was shot over, and his pants were still wet.
In the shot where the camera is on the shark's back as it's heading toward Mike while his friends try to lift him up out of the water, a large crew boat is visible in the background behind one of the sailboats (upper right corner of the screen)
In the very beginning, as Brody travels to the party, an aerial view of the truck reveals the shadow of the camera perched on the railing of the bridge, along with several crew men.
After Brody crashed the police boat into Cable Junction, in the behind shot, shadows of the camera and crewmen can be seen on the stern of the boat, below the word "Police".
When Brody leaves for returning the police car, the shadow of the camera team can be seen on the car side as he pulls away.
When diver is lobster hunting, the lobster shown is a spiny lobster found in warm seas like FL, the Bahamas etc.
Soon after Tina and Ed discover the killer whale carcass by the lighthouse, Brody and Hendricks begin conducting an investigation. There were no radios on any of the sailboats, the lighthouse was unmanned (and possibly without telephones), and the film took place in a time before cell phones were prevalent. Unless someone in the group sailed back to Amity Island to report it, there would have been no other way to contact the police.
When Brody first spots the drift wood, it's in the shallow water near the shore and there's no possible way for a body to be attached to it without being noticed right away. In the next shot, it's in deeper water and it can be seen that there is still nothing attached to it, there is nothing on, in, or near it when he reaches out to grab it.
After the shark first attacks the teenagers, Polo's boat is the only one still capable of sailing because all the others crashed during the chaos. Polo and Timmy then take Mike who is injured back to shore. There was still plenty more room in Polo's boat, so some or all of the others could have also gone back in his boat, rather than being stranded at sea.
When Brody and Ellen are sitting at the kitchen table on the morning after Brody was fired, when Ellen stands up to talk to their house keeper, the shadow of a crewman holding a boom mic is visible on the wall on the right of screen, while the shadow of the boom mic can be seen above the doorway.
The morning after Brody is fired and he is in the kitchen looking at himself in the mirror, just as he turns around when his wife walks in, a boom mic is visible.
Reflected on Ellen's shades when she first notices her husband up in the shark tower.
In "Jaws", Police Deputy Hendricks' first name is Lenny. In "Jaws 2", the same character is addressed as Jeff (which is the actual name of the actor) after Brody is fired. This is the only time in the movie that Hendricks' first name is spoken, and Brody and his wife have called him by his real name instead of his character name.
When the kids go sailing and pass the dive boat, the dive captain shouts to Andy that they're going for lobster. Jackie jokingly shouts back that she wants her lobster "drawn with butter." The correct phrase is "with drawn butter." Drawn butter is melted butter used as a sauce for seafood.
As Tina and Eddie discover the beached killer whale carcass, they seem stunned and surprised. But since they had just come from the light house, they should have been able to see it before running up on it, especially due to its size and the fact that it was out in the open on the beach. And depending on how long it had been there, they might have even been able to smell it.
After Brody fires several rounds at the bluefish, a beach goer sarcastically comments, "Do you think this is Dragnet?"
In the more than 350 episodes of Dragnet, a gun is fired maybe a handful of times, making it an extremely rare occasion, thus contradicting the beach goer's comment.