While on Pirate Island, the sea pups need Stormy's help with a map; that leads to the Cave of Neptune. Stormy heard legends say; that an amazing sea creature lives there, but no one's ever seen it.
Bucky goes undersea, and the crew deploys their own mini subs. Suddenly, they hear a strange noise. The crew and Stormy follow it to the Cave of Neptune, and a baby sea serpent came out. They figured it was his mother who made the noise, they named the baby; Slink. Stormy heard Marina's "lunch bell", and left. Equally, the crew went back to Pirate Island.
There, the crew were talking, when Skully's crackers disappeared. They looked behind a chest, to find Slink. They figured he followed them home, and knew they had to get him back to his mother. After a chase around the Hideout, Cubby used a stick to get Slink's attention for fetch. When Captain Hook, who was spying on the sea pups, saw Slink; he wanted to catch him for his new zoo. Sharky and Bones scooped up Slink in a net, and took him to the Jolly Roger. Cubby sneaked aboard after them, and found Slink. But how was Cubby going to let the crew know where he was. Slink poked hole into the "fetching stick", and Cubby could play a song with it, and he did. On Pirate Island, the crew searched for Cubby and Slink, but couldn't find them. But then, they heard Cubby's flute music from the Jolly Roger, realizing that Cubby had to be there. Stormy heard the song too, and found Cubby on the Jolly Roger. When Cubby told Stormy what Hook was planning, she swam to get help. Hook believed that Slink would be the star beast of zoo, when Jake, Bucky, Skully and Izzy showed up. Then, Cubby rose up from below deck with Slink, Hook said nothing would get him to stop the ship. Suddenly, a loud THUD, bumped the ship. It was Stormy, with Slink's Mother.Hook tried to steer the Jolly Roger away from the sea serpent, but that just made her mad. The sea serpent swam around the Jolly Roger, making it spin away. Meanwhile, Izzy used pixie dust to fly, and rescue Slink and Cubby. Slink, his mother, and Stormy all swam away after that.
Later, on the Jolly Roger, Hook mourned over having no beasts for his zoo. Sharky and Bones tried to cheer up Hook with the news that they found some beasts; the Tick-Tock Croc, and the Orange Octopus(the Treasure with eight arms). much to Hook's horror,as both beasts chased Hook around the ship.