Continuity mistake: Cecilia and Raymond are on the end of the dock and Raymond turns around and runs. Cecilia then says her line, turns around and runs. In the next shot the two girls are running towards the end of the dock. You can see Raymond running towards them but Cecilia is gone. She should be in the scene running the same way.
Factual error: When Cecelia and her friends are in the car, following Aquamarine, Hailey, and Claire to the water tower, they aren't that far away - probably less than thirty feet - yet the other girls don't hear their car approaching.
Continuity mistake: When Cecilia is at the water tower looking for Aquamarine, one or both of her earrings are missing. when she gets back to the beach party she now has both of them on.
Continuity mistake: When Aquamarine is in Leonard's house after he rescued her from the water tower, the tuckshop lady comes down the stairs outside with a basket of washing and walks away. The camera then goes on Leonard and Aquamarine again, before showing the tuckshop lady coming down the stairs again with the same basket of washing and walking away.
Continuity mistake: When Claire and Hailey are watching Cecilia and her friends talk to Raymond, a man and a woman in a white bikini pass by in the background, but after a quick cut to Claire and Hailey, the couple walk by again.
Continuity mistake: During the balloon toss, when Raymond gets wet, the water spot on his shirt changes location three times.
Continuity mistake: When Aquamarine says "Boo!" to Claire and Hailey in the swimming pool, you can see her fin, but in the next scene when Claire and Hailey scream, the fin has gone back under the water.
Other mistake: In the beginning, Aquamarine exclaims "My fingernails! They've never been this color before!" But her nails don't actually change colour until a few shots later.