A persistent rumor haunts the local school's swimming pool—whispers of a supernatural entity lurking beneath the surface, claiming innocent lives particularly after dark. Rather than investigate or publicize the threat, the institution simply seals the facility when daylight fades, hoping discretion will contain the problem. Despite warnings implicit in the locked gates, curiosity and skepticism draw brave or foolish intruders to breach the natatorium at night, where they encounter something far more terrifying than legend suggested, with few ever emerging to tell what they've witnessed.