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.
Aquamarine (2006)
1 other mistake - chronological order
Directed by: Elizabeth Allen, Elizabeth Allen Rosenbaum
Starring: Emma Roberts, Sara Paxton, Jake McDorman, JoJo
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.
Aquamarine: Starfish may be huge suck ups. But they never lie.
Trivia: Throughout the movie, Aquamarine is always eating salt and putting salt in strange things like ice cream. To film these scenes, they had the actress, Sara Paxton, eat sugar instead.
Question: Before Aquamarine showed up, Claire's grandmother told the girls that there was going to be a storm. Later, the girls learn that the storm that night was caused by Aquamarine's father getting angry. How did Claire's grandmother know that there was going to be one, unless she knows Aquamarine's father?
Answer: Because caused by mythical sea-dwellers or not, storms always have telltale signs beforehand, like darkening skies, or the wind changing temperature and strength.
This does not answer the question in the context of the movie. A fantasy situation is happening in a fantasy movie. The realistic answer is not necessarily the correct one.
Answer: Most likely, Aquamarine and her father had argued multiple times, about her not wanting marry the boy that he chose for her. She was going against tradition. Claire's grandmother probably saw storm signs caused by an earlier argument. Then Aquamarine's father got angry enough to make the big storm.