Andrew Stanton built Finding Nemo around the anxiety of parenthood, and Nemo's rebellion is the engine that starts the plot. Marlin tells Nemo not to swim to the boat. Nemo swims to the boat. This is not disobedience for its own sake. It is a child testing the boundary between his father's fear and the actual world, and discovering, as children must, that the boundary is in the wrong place. Marlin's fear is real. A barracuda killed Nemo's mother and all of his siblings. But the response to that fear, wrapping Nemo in so much protection that the ocean itself becomes a threat, is the thing Nemo has to escape in order to grow.

Stanton described the film in a 2003 interview as a father's nightmare played out as adventure. Dr. Peter Gray of Boston College, in his research on self-directed play and child development, has documented that children who are denied the opportunity to take risks develop higher anxiety and lower competence than those who are allowed to test their limits. Nemo's lucky fin, the small deformed fin that Marlin uses to justify his protectiveness, is not a disability. It is a difference, and the film's argument is that the difference does not require the cage Marlin built around it.

The Tank Gang and the Education Marlin Cannot Provide

While Marlin crosses the ocean to rescue his son, Nemo is getting the education his father's fear prevented. In the dentist's tank, Gill teaches Nemo to be brave, to take risks, to trust his own body including the lucky fin. The tank is a prison, but it is also a classroom where Nemo learns the independence his father's love denied him.

The parallel structure is the film's genius. Marlin learns to let go by crossing an ocean of dangers. Nemo learns to be capable by surviving a tank full of them. They meet in the middle, each having become what the other needed: Marlin has become brave enough to trust his son, and Nemo has become competent enough to deserve that trust.

The Lucky Fin

Nemo's fin is never healed. Pixar does not fix the disability. Instead, the film demonstrates that the fin is only a limitation when Nemo believes it is, and that belief was taught by fear, not by experience. When Nemo swims down to save the fish from the net at the film's climax, he uses the fin he was told could not do enough. It does enough. It always could.