During the scene when Craig joins Alyssa and Rasca the dolphin in the water, Alyssa's bikini bottoms change from blue shorts to orange bikini bottoms and back again, because a shot from the opening scene with Rasca was reused.
Right after Craig jumps off the boat to join Alyssa and the dolphin, there is a brief shot where the boat's name is reversed.
When Gwen is on the boat the film is reversed most of the time we see her close up. The writing on the driver's cap, her mole and her watch are all reversed. On the overhead shots you can see her standing behind and to the left of the driver, but in all but one close up she is on the right.