It's hard out there for a tween.

With Hollywood focusing laser-like on either G-rated kids' cartoons that make a zillion in DVD sales, or horror flicks and sex comedies that keep those cherished 17-year-olds coming back for repeat business in theaters, 10- to 13-year-olds -- especially girls -- are often left behind. What's more, appealing to their singular sensibilities, which teeter between schoolgirl innocence and burgeoning sophistication, is a difficult needle to thread.

At least "Aquamarine" tries. Based on Alice Hoffman's novel of the same name, the mild-mannered comedy tells the story of 13-year-old best friends Claire (Emma Roberts) and Hailey (Joanna "JoJo" Levesque), who discover something strange in their beach club's swimming pool after a bad storm: a mermaid named Aquamarine (Sara Paxton), who has come ashore to find true love. She immediately sets her baby blues on a lifeguard named Raymond (Jake McDorman), whom Claire and Hailey have been crushing on all summer.

The direction, by Elizabeth Allen, isn't particularly distinguished, and there are no stand-out performances to speak of, even from pop star JoJo making her big-feature debut (someone should put her in a movie as Lindsay Lohan's little sister). Still, "Aquamarine" is better than nothing for its woefully underserved audience.

-- Ann Hornaday

Contains mild profanity and sensuality.