Although Kaori Sawahara, a college student, expected her trip to Okinawa to be a pleasant seaside getaway, the reality proves far from it when a terrifying threat rises from the ocean depths. An odd device has seized control of marine life, equipping them with legs and driving them onto land to assault anything they encounter. Kaori and her companions—the sexually driven Erika and the quiet Aki—are swept up in this assault, which is intensified by the creatures' putrid odor of decay. After surviving the initial attack, Kaori attempts to reach her fiancé Tadashi in Tokyo. Yet, the phone call is abruptly ended, seemingly due to another fish attack. Worried about his well-being, Kaori departs for Tokyo. While Erika and Aki deal with the attacks in Okinawa, Kaori hurries to locate Tadashi, oblivious to the fact that the crisis has merely begun.