Errors in geography: When they are on the beach there are mountains in the background. There are no mountains in Florida.
Factual errors: In two underwater shots showing sharks attacking the camera, the sharks portrayed are grey reef sharks, not tiger sharks. Tiger sharks are a lot bigger and have a striped pattern on their backs.
Continuity: When the three kids are in the boat, the shark attacks the boat and Danielle bumps into the harpoon shooting Shane in the shoulder. In subsequent shots, before Danielle pulls it out, the tip of the harpoon (which is first shown coming out of his back) is either missing or bent.
Revealing mistakes: In the scene where the three girls are walking on the beach after Danielle first arrives in Florida, Danielle's hair is up in a bun. The camera cuts away, then is back on the girls and her hair is down.