It sneaks up on you. Forty-odd minutes of a drowned world, a kid, and her grandfather, and then a final scene that reviewers admit they still carry around decades later. The setup is simple enough for an eight-year-old: oceans swallowed the continents, Elfie's city-island is one of the last scraps of land, and one underwater accident tells her she was never fully human to begin with. What makes it stick is what the adults do next, politicians farming the city's fear of the sea-people into an actual war because a monster is easier to sell than an apology for the flood. The 1986 animation is plain and the plot never gets clever, and honestly that's fine. It knows exactly which moment to spend everything on, and it spends it on Elfie choosing which world she belongs to.

Humanity's carelessness has drowned the world. Rising seas consumed every continent, leaving only scattered islands where survivors cling to existence. Elfie lives on one such island city with her grandfather. When an accident beneath the waves reveals that she can breathe underwater, her grandfather tells her the truth: she is one of the legendary sea-people. As the island struggles with shortages, local politicians exploit the townsfolk's distrust of outsiders and stir up a war against this hidden race to divert attention from their troubles. With plans to expand undersea ranches threatening a repeat of past mistakes, Elfie finds herself caught in the middle of the conflict.