Based on the book by Alice Hoffman (PRACTICAL MAGIC), the refreshingly innocent AQUAMARINE follows two 13-year-old best friends through the last days of summer. Claire (Emma Roberts) and Hailey (Joanna "JoJo" Levesque) are inseparable, sharing everything including a crush on lifeguard hottie Raymond (Jake McDorman). But their days of carefree giggling will soon come to an end if they can't find a way to stop Hailey's imminent move to Australia. Unexpectedly coming to their rescue is Aquamarine (Sara Paxton), a mermaid who appears one day at the beach-club that Claire's grandparents own. Emerging from the pool with long blonde hair, eyeliner, and sass, the mermaid possesses everything Claire and Hailey lack--confidence, big breasts, and nail polish that changes color with her mood. If the girls can get Aquamarine (whose fin transforms into long legs on land) used to life among humans and help her find true love, they may get their wish granted for Hailey to stay. Putting their personal feelings towards Raymond aside, the girls attempt to set him up with the mermaid despite interference by a villainous girl who wants Raymond for herself.

When the girls aren't on the beach, they're shopping or having sleepovers in bedrooms covered with the marks of teen girlhood: pink bedspreads, pictures of celebrities, and an endless supply of teen magazines. The film's funniest moments come from the characters' attempts to not only master the magazine's many absurd prescribed techniques for getting boys' attention, but also from their having to teach a mermaid to do the same. While the film doesn't exactly argue with the messages spouted by publications like CosmoGirl, it brings them into question by highlighting just how centrally they factor into shaping the "tween" generation. It also suggests true friendship may be more valuable than perfect looks or popularity.