Pisces, or Pi (Freddie Prinze, Jr.), is a 5-year-old orange fish that lives happily with his parents Pike and Piper in the polluted harbor of Boston, Massachusetts, until a fishing boat scoops them from the sea. Pi's parents manage to help him escape, but cannot escape themselves. Before Pi's parents are taken away, Piper tells Pi to promise her he would go live with his aunt. Pi's porpoise friends Percy (Trent Ford) and Percy's mother Meg (Megahn Perry) agree to take him, but Pi refuses to leave in case his parents return, Meg sadly tells him that once anyone is taken by a net they can never come back; Pi feels depressed knowing he is now an orphan. Meg and Percy take Pi to live with his aunt Pearl on an exotic reef. When Pi reaches the reef, he is 18 years old and has stayed with the porpoises for most of his life. As he tries to settle himself in this new world, the sweet and well-meaning Pi makes some good friends in his new home, the first residents Pi comes across are three elderly marlins named Moe, Jack, and Manny, which direct him towards Pearl's home. On his way there, Pi immediately falls in love with Cordelia (Evan Rachel Wood), a celebrity fish that has appeared on the front cover of National Geographic. He also meets his cousin Dylan (Andy Dick), that quickly becomes Pi's best friend.
However, Troy (Donal Logue), the meanest, toughest tiger shark in the ocean, is not only terrorizing everyone in the reef community, but also has his eye set on Cordelia to become his mate. Pi confronts Troy, only to have him smack Pi with his tail. Cordelia tells Pi that Troy is her problem, and to not interfere. Pi and Dylan find their way home, where Pearl (Fran Drescher) is excited to see that Pi has arrived. She is a fortune teller using a pink pearl that Dylan's deceased father gave to her. Pearl reads Pi's future and is surprised, saying that he is destined for great things and that the reef is the best place he will be able to find it. While out on a swim with Pearl and Dylan, Pi is told by Dylan about Nerissa (Rob Schneider), a wise old hermit turtle that lives in the Old Ship Wreck and practices martial arts, leading to rumors that he is a wizard.
When Pi helps Cordelia after she gets a hook in her fin, she invites him to go to a concert with her. Beforehand, Pi meets Dylan once again and they observe Nerissa defend his blue pearl using the sea from a gang of squid robbers. At the amphitheatre that night with Cordelia, Pi learns about the performer Thornton (John Rhys Davies) a harbor seal that tangled with a large creature. Afterwards, Pi and Cordelia look at the stars and she falls in love with him. Suddenly, an enraged Troy arrives and starts abusing Pi worse than ever, until Cordelia makes a deal with him: if he leaves Pi alone, she will marry Troy (which, in this case, is done when someone "accepts someone else's pearl"), Pi is knocked unconscious by Troy and is carried to Nerissa's shipwreck by a current.
When Nerissa tells Pi the following day, he decides he has had enough of Troy's abuse towards him, and asks Nerissa to teach him the ways of the ocean to combat Troy. Nerissa refuses, telling Pi to fight his own battles. Pi asks other residents to help him, but the marlins are too afraid and think because of their age, they wont be useful. Pi asks Thornton, he states Pi must be crazy, Pi only reminds Thornton of his tale of his encounter with a sea monster. However, he states that he did not actually fight a monster, but since he said it in rhyme, it did not count as lying. Meanwhile, Troy's henchmen Bart and Eddie try to steal Nerissa's pearl, but are frightened away by Pi and Dylan. Nerissa arrives and is impressed with Pi's skills, agreeing to train him the next morning.
On Pi's first day of training, Pearl tells Pi that she could not live with herself if Pi were killed. Pi then reminds Pearl how she said that he would find his destiny on the reef, and he did when he met Cordelia. Stating now he is about to lose her just like how he lost his parents, Pi tells Pearl how he could not do anything to save them, and maybe he could not save Cordelia, but he will not give up without trying. Nerissa starts by telling Pi that Troy picks on anyone smaller than him, and he has never learned about things bigger than him, Nerissa says the ocean itself is bigger than Troy and if Pi can use the ocean against him, his own size would not matter. Nerissa leads Pi down a valley with obstacles, including razor-sharp elkhorn coral, burning fire coral, a long, narrow tunnel known as Bottleneck Alley, and finally a current known as the West Indies current, full of Portuguese man o' war that could kill someone Pi's size.
Meanwhile, Cordelia is informed by Buddy the decorator crab and Lou the sawfish about Pi's upcoming battle with Troy. Nerissa reveals the story of his blue pearl to Pi and he gave it to his wife, but she got hooked in the open sea. Nerissa desperately tried to call for help, but no one was brave enough to help. Pi understands, but wonders how he can stop Troy for good; Nerissa tells him to offer Troy something he wants and then give him something he doesn't want. Cordelia finds Pi and repeatedly tries to convince him to reconsider, believing what's done is done. That night Pearl's pearl has been stolen by Troy's henchmen. She is heartbroken, being as Dylan's father gave her the pearl. Pi realizes that he cannot back down now no matter how much everyone else doubts him.
After mastering the ways of the ocean, Pi's friends Thornton, Buddy, and Lou, and Moe, Jack, and Manny (three marlins that were friends of Nerissa's), Cordelia and Dylan decide to band together to stop the abuse and terror that has caused fear within the reef's population. After training his friends, Pi leads the charge and they deal with Troy's crew in a final showdown.
Pi initiates a chase with Troy. As Pi swims away from Troy through the valley Nerissa instructed him to take, Troy is hit by all of the obstacles until they get to the open sea. Nerissa tries to help by throwing an old boot at Troy's henchmen Bart and Eddie, and Dylan shoves them down a lobster hole, retrieving his mother's pearl in the process. Pi is then swatted by Troy's tail into a cliff, burying him in rocks. Nerissa attempts to help him, but is hit by Troy; just as all seems lost Moe, Jack, and Manny arrive to fight Troy and apologize to Nerissa for not having his back when he needed them.
Percy and Meg return and free Pi. Troy then sets Percy as a target. Pi distracts Troy long enough to allow Percy to escape. Troy targets Pi and chases him up to the surface, where he manages to lead Troy into a fishing net and narrowly escapes the shark's jaws as he leaps through the top of the net. Troy, trapped in the net, is lifted from the sea. Pi is proclaimed a hero by the population of the reef. Nerissa gives Pi his pearl because Nerissa sees Pi as his son and if he had one himself he would have given it to him. Pi is honored and does not know what to say. Nerissa states that Pi knows exactly what to say, but he is just not the one to whom he needs to be saying it. Cordelia accepts the pearl that Pi gives her and they share a kiss as the reef celebrates, along with Bart and Eddie, which rejoice that they are all free from Troy.
In a mid-credits scene, Thornton tells Pi's story to everyone on the reef, proud now that he can tell a true story about himself ending with "Pi was determined, he refused to despair, I know it's all true, for you see, I was there..."Freddie Prinze, Jr. as Pi (Pisces), a male orange wrasse fish, orphaned when his parents were caught in a fishing net
Evan Rachel Wood as Cordelia, a female pink angelfish model for National Geographic and Pi's love interest
Rob Schneider as Nerissa, an old widowed hermit loggerhead sea turtle and Pi's mentor
Schneider also voices Bart and Eddie, Troy's henchmen, Bart is a smart, sophisticated barracuda, while Eddie is a dim-witted wolf eel. Schneider also voices other characters.
Donal Logue as Troy, a tiger shark that terrorizes the entire population of the reef and Pi's chief nemesis
Andy Dick as Dylan, a teal fish and Pi's cousin
Fran Drescher as Pearl, a purple fish that is Dylan's mother and Pi's aunt and adoptive mother, she is a fortune teller.
John Rhys Davies as Thornton, an elderly harbor seal that is very poetic
R. Lee Ermey as Jack an overweight marlin
Jimmy Bennett as Young Pi
Dylan Cash as Young Percy
Richard Epcar as Moe, an elderly marlin
David Fickas as Max, a flamboyant crab that is Cordelia's boss
Trent Ford as Percy, a porpoise that is Pi's adoptive brother for 13 years
Joel Michaely as Lou, a sawfish and Buddy's assistant
Megahn Perry as Meg, Percy's mother, Pi's surrogate mother
Mel Rodriguez as Manny, a flatulant Spanish marlin
Lena Gleen as Buddy, a flamboyant decorator crab and Lou's boss
Bruno Alexander as Pike, Pi's deceased father
Reedy Gibbs as Piper, Pi's deceased mother
Kim Hyung-jun as Pisces ("Pi")
Kim Kyu-jong as a clam and a crab
Kim Hyun-joong as a crab
Park Jung-min as a dolphin
The reviews of this film were largely negative. It has been berated as a 'Finding Nemo rip-off' as it heavily borrows from the film, as well as borrowing from other films such as Shark Tale and Karate Kid. It was also criticized for its poor animation and its visuals which were considered outdated.
eFilmCritic.com's David Cornelius described it as "undoubtedly one of the cheapest, ugliest cartoon features ever produced", criticizing its CGI, graphics, and animation. He also criticized its plot, saying, "the script also rehashes every conceivable cliche the kid flick book".
Vince Leo from Qwipster's Movie Reviews gave the movie 2 out of 5 stars, saying, "Shark Bait (aka The Reef in some markets) certainly is testing the limits. It's easily the worst CG-animated adventure to date (up to 2007), burdened with lame puns...". He criticized the animation, calling the character designs "lackluster" and the background "overly simplistic".Richard Epcar – voice director