When a surfie sea ghost insists that Megan and Abi find his missing leg, the gang suddenly find themselves shark hunting. It is the Festival of the Sea on Paradise Island and Abi and Megan are both desperate to win the smoothie-making competition and the accompanying big cash prize. Marty, a surf dude sea ghost who lost a leg in a shark attack, hops up to find his missing limb. He is very competitive and manages to bring out the worst in Megan and Abi, who will stop at nothing to beat each other. Marty thinks he has a secret ingredient guaranteed to make the best smoothie ever, but he will only reveal it to the one who finds his leg. The trouble is, it is still stuck on the shark's fin. Tai revisits a place from his dreams and comes face to face with Ragnar who tells him he is the Sea Born, with some extra-special powers. Tai must make some big choices as he decides whether to use these powers for good and help the gang find Marty's leg, or be tempted to get selfish and succumb to the evil Ragnar.