Continuity: 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.

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: During the balloon toss, when Raymond gets wet, the water spot on his shirt changes location three times.

Continuity: Near the end, when Aquamarine (as a mermaid) is talking to Raymond on the surfboard, her wet hair drastically changes between shots.

Continuity: 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.

Continuity: 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: 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: In the beginning, Aquamarine exclaims "My fingernails! Look at them!" or something along those lines. But her nails don't actually change colour until a few shots later.

Continuity: Throughout the entire film, Aquamarine's blue streaks change from being very light to much more pronounced.