The size and breed of the shark changes throughout the course of the film. At one point, it's a tiger shark, then it's a massive great white.
At 40.00, the helicopter pilot takes his hand off the throttle and points out the window at the shark- he would lose control of the helicopter.
Sometimes the shark is clearly a dolphin.
At 40.10, when shooting at the shark, he jerks back the gun, to simulate the recoil, but doesn't actually pull the trigger.
When she's being pulled from the water the "paralyzed" girl wildly kicks her legs.
Before the windsurfing regatta, there are a group of cheerleaders that say, "Lewis Number One". If you look though, they clearly spell out "Wells".