While working together to restore power to the underwater Neptune City, Jake, Cubby, Izzy, Skully and Marina discover that Bucky has the ability to turn into a submarine. Meanwhile, Captain Hook and his bumbling crew are looking for the Jolly Roger's missing anchor, when Hook witness Jake and crew dive below the depths of the Never Sea. Hook and Mr. Smee soon follow, using diving suits to discover what ever undersea treasure they may be after.
As Jake and his crew explore the wonders of the depths of the Never Sea, they discover that a Pink Pearl was knocked out of the Neptune statue's hand, and replaced by the missing anchor of the Jolly Roger. While Marina and the sea pups try to restore the pearl to its resting place, they run into Captain Hook and Mr. Smee, who were originally on the hunt for the missing anchor, but Hook couldn't pass up a chance to swipe the pearl from the puny pirates, but was thwarted yet again by the young pirate team and sent fleeing back to the Jolly Roger along with Smee and the missing anchor with a hungry shark in pursuit. This allowed Marina to restore the pearl back to the statue, and the warm glow of the Pink Pearl called the mermaids back to their home.