Marlin (a clown fish) is a widower who only has his son Nemo left of his family after a predator attack. Years later on Nemo's first day of school he's captured by a scuba diver and taken to live in a dentist office's fish tank. Marlin and his new absent-minded friend Dory set off across the ocean to find Nemo while Nemo and his tankmates scheme on how to get out of the tank before he becomes the dentist's niece's new pet.