Oscar (Will Smith-voice) is a little fish working in the whale-wash as a tongue washer, the bottom of the fish organizational chart. Oscar dreams of becoming a somebody some day and living at the top of the Reef. Oscar has been getting advances on his wages from his boss, Sykes (Martin Scorsese-voice) a puffer fish, to bet on the seahorse races. Don Lino (Robert DeNiro-voice) is the great white shark mafia boss at the top of the Reef's food chain, who wants his two sons, Lenny (Jack Black-voice) and Frankie (Michael Imperioli-voice), to take over the business. Don Lino orders Sykes to pay what he owes him. In turn, Sykes orders Oscar to pay the 5,000-clams debt he owes him. Oscar is able to get the clams from his best friend, Angie (Renee Zellweger-voice), who has a secret crush on him. Oscar is supposed to pay Sykes at the racetrack; regrettably, Oscar makes a 5,000-clam bet, and Sykes ends up ordering his jellyfish to take Oscar out. Frankie is about to eat Oscar when he is hit and killed by an anchor. Oscar takes credit for killing the shark, and he becomes the Sharkslayer and protector of the Reef. Lenny, a vegetarian, becomes Oscar's friend and helps him with the charade. Don Lino is out to avenge his son's death by ordering all the sharks to find and eat Oscar.