Revealing mistake: When Nick has swam back to his water scooter, he climbs up and drives away and the shark comes up behind him. But look carefully behind Nick as he is climbing. The nose of the shark is visible during the whole scene, right under the surface. This proves that the shark was a dummy, waiting to come up.
Revealing mistake: During the surf competition, while Tom is swimming away from the sharks, the water is calm, suggesting this scene was shot in a lake or pool. You can see it again while Nick is swimming back to his jet swimmer.
