Twelve years ago, Otta escaped her small town, determined to become a marine biologist. Now she’s returned, carrying the guilt of a friend’s disappearance during a deep-sea dive and unsure she’ll ever be able to dive again. Then a stranger appears at her door. This stranger, May, says that her daughter has run away, and insists that she’s under the nearby lake --- alive. To find the missing girl, Otta and May must travel deeper and deeper beneath the water, confronting webs of fear, control and delusion borne of a rampant nostalgia for a purer world. Along the way, they will also push their bodies to the mortal limit.