Continuity mistake: After Barry has jumped into the water reclaim the crown, he comes out of the water with a perfectly clean shirt but in the next shot the blood is back on his shirt as expected.
Continuity mistake: Max lies dead in Julie's car covered in crabs. He was hooked very deep under his chin, yet when we see him, the wound is gone.
Visible crew/equipment: When Julie comes home at her mothers house, she looks at her diplomas on the wall. When her mother comes in the room, you can see a reflection of a boom mike in the frame behind Julie.
Deliberate mistake: The film supposedly took place in the Coastal Carolina region. This is a geographically flat area, called a coastal plain. In the beginning of the film, the kids were driving along ocean cliffs, which are not present in the Carolinas. Obviously, this was filmed in California.
Revealing mistake: Portion of the film were shot at an old farm house. The trees were bare, without leaves. Obviously filmed in the winter.
Revealing mistake: When the killer is dragging the girl's body with the meat hook, you can easily see that it is a doll.
Factual error: Near the end, Julie James is crouching down by the front tip of the boat with a flare gun in her hand. Now, she is crouching so she is looking straight at the rest of the boat, instead of looking over the front of the boat. Then Ben Willis starts the boat with a big push and she falls back against the tip of the boat and the gun flies out of her hands. Now when you do that with a car, you normally fly backwards, but since Julie is turned around the other way, she should fall onto the piece of boat in front of her.
Factual error: When JLH visits Missy at her home Missy says she went to Southport High, but in the July 4th celebrations the marching band has a banner which reads East Brunswick High School. A bit strange that a "small fishing village" would have two high schools for the simple fact that well the town probably couldn't afford it and it's pointless to have two when the village is so small. Factually, Southport does indeed have just one high school - South Brunswick High. See http://schooltree.org/NC-BRUNSWICK.html.
Plot hole: Barry gets killed violently at the pageant. So obviously there should be blood everywhere. When the police go up to the crime scene, they find nothing. There's no way the killer had time to clean up anything, let alone drag away Barry's body without someone seeing him. And blood starts dripping after the police leave the scene.
Continuity mistake: When the Fisherman jumps out at the girl in the store when he is in the plastic bag, he misses and falls to the floor. If you look at the Fisherman when he is on the floor and waving his arms notice he isn't carrying his hook. However, in the next shot when he is standing up, the hook is in his hand again.
Continuity mistake: When Julie comes home and finds the letter, her lips are pale and she is not wearing lipstick. When the shot shifts focus from the letter to her face again, however, she is wearing purplish lipstick.