The story begins with an underachieving fish named Oscar, who is fantasizing about being rich and famous ... while making his way to work as a tongue scrubber at the Whalewash, a business much akin to a car or truck wash.
Meanwhile, on another side of the ocean, a family of criminally-inclined sharks has a problem with one of their sons, Lenny. Lenny refuses to act the part of a killer and wishes to not have to live up to those expectations. With this, his father, Don Lino, decides that he must learn to kill, by being taught by Lenny's more savage brother, Frankie.
As the two sharks set out to go in accordance with their father's wishes, Frankie spots the scene where Oscar is being electrocuted by Ernie and Bernie, Sykes' two Jamaican jellyfish thugs, and sends Lenny off to attack. The jellyfish spot Lenny and swim off, leaving Oscar alone with him. Lenny tries to calm Oscar down by telling him that he will not eat him, but Oscar will not listen and continues on screaming. Frankie becomes annoyed and tries to attack, but suddenly an unknown anchor falls and kills him. Lenny is panged with guilt and flees.
As no one saw the deed done and Oscar was seen near the body, everyone thinks he did it, and Oscar sees this as the chance to both redeem himself and receive his fame.