Two clownfish, Marlin and Coral, admire their new home in the Great Barrier Reef and their clutch of eggs when a barracuda attacks, knocking Marlin unconscious. He wakes up to find that Coral and all but one of the eggs have been eaten by the barracuda. Marlin names this last egg Nemo.
Nemo develops a smaller right fin due to damage to his egg, which limits his swimming ability. Worried about Nemo's safety, Marlin embarrasses Nemo during a school field trip. Nemo sneaks away from the reef and is captured by scuba divers. As the boat departs, a diver accidentally knocks his diving mask overboard. While attempting to save Nemo, Marlin meets Dory, a good-hearted and optimistic regal blue tang with short-term memory loss. Marlin and Dory meet three sharksÂ â Bruce, Anchor and ChumÂ â who claim to be vegetarians. Marlin discovers the diver's mask and notices an address written on it. When he argues with Dory and accidentally gives her a nosebleed, the blood causes Bruce to enter a violent feeding frenzy. The pair escape from Bruce but the mask falls into a trench in the deep sea.
During a hazardous struggle with an Anglerfish in the trench, Dory sees the diving mask and reads the address located at 42 Wallaby Way, Sydney. Marlin traps the Anglerfish using the eyepiece of the mask. To her own disbelief, Dory is able to remember the address on her own despite her short-term memory loss. The pair swims on, receiving directions to Sydney from a school of moonfish. Marlin and Dory encounter a bloom of jellyfish that nearly kills them. Marlin loses consciousness and wakes up on a sea turtle named Crush, who takes Marlin and Dory on the East Australian Current. Marlin tells the details of his long journey with a group of sea turtles, and his story is spread across the ocean. He also sees how Crush gets along well with his son Squirt.
Meanwhile, Nemo is placed in a fish tank in the office of Phillip Sherman, a dentist. He meets aquarium fish called the Tank Gang, led by Gill, a moorish idol. The fish learn that Nemo is to be given to Sherman's niece, Darla, who previously killed a fish by constantly shaking its bag. Gill then reveals his plan to escape, jamming the tank's filter. The fish would be placed in plastic bags so that Sherman can clean the tank, and then they would roll out the window and into the harbor. After an attempt at the escape goes wrong, a pelican, Nigel, brings news of Marlin's adventure. Inspired by his father's determination, Nemo successfully jams the filter, but Sherman installs a new high-tech filter before they can escape.
After leaving the Current, Marlin and Dory are engulfed by a blue whale. Inside the whale's mouth, Dory communicates with the whale, which carries them to Port Jackson and expels them through his blowhole. They meet Nigel, and he takes them to Sherman's office. Darla has just arrived and the dentist is handing Nemo to her. Nemo plays dead to save himself as Nigel arrives, causing Darla to scream. Upon seeing Nemo, Marlin mistakenly believes he is dead, before Nigel is violently thrown out. In despair, Marlin leaves Dory and begins to swim home. Gill helps Nemo escape into a drain that leads to the ocean. Dory loses her memory and becomes confused, and meets Nemo, who reaches the ocean. Eventually, Dory's memory returns after she reads the word "Sydney" on a drainpipe. She reunites Nemo with Marlin, but she is caught in a fishing net with a school of grouper. Nemo enters the net and orders the group to swim downward to break the net, enabling them to escape. After returning home, Nemo leaves for school, with Crush's son Squirt, and Marlin and Dory proudly watch Mr. Ray carry Nemo and his friends to school.
In a mid-credits sequence, the high-tech filter in Sherman's tank breaks down, and the Tank Gang escape into the harbour. Bloat realizes that they now have to find a way to get out of their plastic bags.
What is Nemo?
A fish