The Great Barrier Reef is inhabited by colorful fish called clownfish. One of them, Marlin, meets a tragedy. The predatory fish devours his wife Coral and almost all the eggs from which the young clownfish were to hatch any day now. Little Nemo, the only surviving son of Marlin, becomes the meaning of his life. But when his overprotective father decides to send him to school, another misfortune occurs: the little clownfish is fished out of the ocean by a diver and ends up in an aquarium at a Sydney dentist's office. Marlin, although suffering from fear of the open ocean, sets out to save her son. He is accompanied by the great forgetful Dora.