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.
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.
Danielle follows Shane into the bookstore. Shane at one point picks up a book and the camera moves to focus on Danielle and when it pans back to Shane he is holding a much larger, different book. The first book is nowhere in sight.
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.
After the sharks attack the boat that Shane, JT, Karen, Alicia, and Danielle are on, JT is trying to call the Coast Guard. In the last of three shots, he is holding the mic backwards before slamming it down.
When they are on the beach there are mountains in the background. There are no mountains in Florida.