Australian teenager Kirra is sent to stay with her grandfather, Gus in his run-down amusement park in Cape Town, South Africa after her father was hospitalized for six weeks. Upon arrival, Kirra is met at the airport by Mansa, one of her grandpa's employees. Kirra is initially unhappy about leaving her father, but she eventually makes friends with a boy named Sifiso.
After a fierce storm, a baby male orca was separated from his pod, and became stranded in a lagoon on Gus's property. The next morning, Kirra discovers the animal and names him Willy. Willy proves to be a big hit amongst the park visitors. However, Kirra is concerned about Willy, who is not eating due to stress. Kirra sets herself a mission to take care of it. Kirra tries very hard to get Willy to eat a fish, and finally succeeds after talking to him about her parents.
Gus' competitor Rolf Woods learns about the new attraction at Gus' park, and offers to buy Willy for $500,000, but no deal is made. After much perseverance, Kirra persuades Gus to call the marine rescue center for help in rehabilitating Willy back into the sea. However, Willy had under-developed echolocation skills and is unable to survive without his pod, thus making him unsuitable for rehabilitation. Not one to give up, Kirra does much research on how to train Willy to use his echolocation skill, despite being told that there is no known method to do so. She then tries to feed Willy blindfolded, but fails many times.
Rolf, desperate for Willy, hatches a plot to poison Willy to get Gus to sell it at a cheaper price. After his plan fails, Rolf denies all knowledge of the plan, though he offers to buy Willy again.
Kirra then camps out by the lagoon to keep Willy calm after the failed plot. Willy suddenly wakes her up, pulls her into the water, and lets her ride him. After that, Kirra and Willy become a double-act at the park, attracting many reporters and cameramen. The money earned from this publicity is then used to fund the fishes needed for Willy's echolocation training. After many tries, Willy learns to use his echolocation, and manages to catch live fish swimming in the lagoon. In the meantime, Rolf returns to tempt Gus with a lower offer for Willy. Faced with a mounting food bill, Gus agrees to sell Willy to Rolf at 500,000 dollars, and insists the exchange take place after Kirra's departure.
Mansa makes an underwater recording device to record Willy’s sounds, hoping to use the sounds to locate Willy's pod. Despite working hard for days, they do not produce any results. One day, Sifiso invites Kirra to go to his Uncle Rudy's safari park to take her mind off Willy. On their way back, they see a billboard advertising Willy as a new attraction to Rolf's theme park. The pair then hurries back, but was too late as Gus had already signed the agreement to sell Willy. Kirra is heartbroken, and makes Gus promise to make sure that Rolf takes good care of Willy. Later, when Kirra goes down to the lagoon, she sees Willy’s pod. However, Gus does not believe her account.
Kirra and Sifiso go to seek Uncle Rudy's help with their plan to put Willy back into the ocean. However, he is not around, but the two steal a crane truck and drive it back to Pirate's Cove. Later, Gus agrees to help them get Willy back into the ocean if his pod can be found. Kirra and Sifiso then head for the harbour with Willy, while Gus and Mansa stay to distract Rolf, who was on his way over. Eventually they find Willy's family, and Willy is reunited with them. Kirra later jumps into the water to bid Willy farewell.
On the day of Kirra's departure, she says goodbye to Mansa and Sifiso at the airport, and agrees to come back next summer. As she gets on the plane, Gus wipes away a tear. Kirra smiles as she takes a final look on Cape Town. Meanwhile, Willy and his pod swim off into the ocean depths.Bindi Irwin as Kirra
Beau Bridges as Gus, Kirra's maternal grandfather.
Siyabulela Ramba as Sifiso
Bongolethu Mbutuma as Mansa
Stephen Jennings as Rolf Woods, the owner of a rival theme park to Pirate's Cove.
Kevin Otto as Dr. Sam Cooper, Kirra's father and a veterinarian. He was injured in an unfortunate accident while tending to the animals.
Darron Meyer as the doctor of Kirra's father.
Jeanne Neilson an air hostess.
Robert Spencer as the nerdy boy.