Claire (Emma Roberts) and Hailey (Joanna Levesque) are two 13-year-old best friends who embark on the adventure of their lives when they discover a mermaid named Aquamarine (Sara Paxton) in a swimming pool. Aquamarine washed ashore after a big storm battered the small town Florida beach club where Claire lives with her grandparents. Claire and Hailey are trying to come to terms with Hailey's impending departure: She's moving to Australia with her marine biologist mother after this last weekend of the summer.
The beautiful, blue-haired, 18-year-old mermaid swam away from home just before her arranged marriage, in search of real love. If she can prove to her father that love is not a myth, he'll let her out of the underwater wedding, but he's only giving her three days. Aqua enlists the help of Claire and Hailey, who are self-styled relationship experts -- educated from the pages of magazines that they read and quote daily.
Aqua sets her sights on the Capri Club's lifeguard, Raymond Calder (Jake McDorman). And when Aqua promises to grant Claire and Hailey the wish of their choice if they help her reel in Ray, the girls jump at the opportunity -- because unless something magical happens, Hailey will be moving.
Prepping Aquamarine on the finer points of attracting a man is easier said than done. And with mere days until the Capri Club's Last Splash end-of-summer celebration, at which Raymond must profess his love for Aquamarine or no one will get their wish, the girls pool their knowledge and give Aquamarine a crash course in terrestrial romance. This includes such surefire techniques as "The Laugh and Pass," and "The Fluff and Retreat." Then there's a hair makeover and a new wardrobe for Aqua -- and dealing with the machinations of Cecilia, Aqua's chief competition for Raymond.
Based on the novel by Alice Hoffman.