Hailey (Joanna "JoJo" Levesque) and Claire (Emma Roberts) are best friends in a small beach community. It's the end of summer, and Hailey's set to move to Australia with her marine-biologist mother. She spends her days with orphaned Claire, who lives at her grandparents' hotel. Viewers are left to puzzle out their potentially touching backstory on their own, as director Elizabeth Allen opts not to explore the girls' actual relationship but to present it as a given.
One night, a storm washes a mermaid (Sara Paxton) into the hotel swimming pool, and she hits it off with the girls. Aquamarine, as the half-human is called, telegraphs wide-eyed vacuity, and though she displays a few moments of comic inspiration, the film isn't particularly interested in her fish-out-of-water tale until very late in its going.
Aquamarine, it turns out, is a runaway bride defying her father's wishes. Determined to prove that true love exists (mer-people believing as they do in arranged marriages), she decides to win the love of beach-boy Ray (Jake McDorman) in the three days she has on land. In exchange for a favor involving their future, the girls agree to help, and soon the proceedings devolve into Mean Girls meets Splash, as Hailey's arch rival, Cecilia (Arielle Kebbel), who also wants Ray, determines to expose Aqua's secret.
An adaptation of Alice Hoffman's juvenile novel, Aquamarine comes off as a ragbag of other people's inspirations. That said, it will likely please its undemanding tween audience -- especially if today's kids are as unsavvy a crew as 20th Century Fox seems to think. But the movie ultimately is divided against itself; it finds its strength in a genuinely nice finale built on the girls' bond, but the plot insists that our heroes care for handsome Ray enough to follow him around, annotating his every move. They consult a stack of teen-girl magazines in search of romantic advice for Aqua, followed by a shopping-mall montage in which they burn through all of Hailey's savings in exchange for a makeover for each of them. Growing up, the film seems to say, means becoming a bubbleheaded consumer.