Dubbed a "pink musical," Underwater Love brings together two genres—musicals and pinku eiga (pink films, a soft-core porn genre of Japanese cinema)—in a story of unrequited love with the mythical water creatures known as kappas. Thirtysomething Asuka has an easy life, a job in a fish factory, and a fiancé, Taki, who's also her boss. One day, as she walks by the lake near the factory, she sees her first kappa—a legendary Japanese creature with a human form but a beak face and a tortoiseshell back. She soon realizes that the kappa is her old friend from school, Aoki, who drowned when he was 17. As she hides Aoki from her fiancé and others, she must begin to decide what is most important for her.

Between Asuka's self-discoveries are some requisite—and outrageous—sex scenes and musical dance numbers with music by French-German duo Stereo Total. Director Shinji Imaoka, part of the new wave of pink directors known as the "Seven Lucky Gods," collaborates with renowned cinematographer Christopher Doyle, who shot many of Wong Kar-wai's films, to create a wacky, silly, touching, sexy spectacle like none other.