Marlin, a clown fish, is overly cautious with his son, Nemo, who has a foreshortened fin. When Nemo swims too close to the surface to prove himself, he is caught by a diver, and horrified Marlin must set out to find him. A blue reef fish named Dory -- who has a really short memory -- joins Marlin and complicates the encounters with sharks, jellyfish, and a host of ocean dangers. Meanwhile, Nemo plots his escape from a dentist's fish tank.