The pirates are back! And the fate of the world is at stake...In Aelenium, the mysterious coral city, Jolly and Munk - the only two polliwiggles left - find out just why they are so important. Together, they must seal the Rift in the sea-bed, or the Maelstrom will break through and destroy the world.To do this, they are trained in shell magic, and in breathing underwater - a vital polliwiggle ability. But Jolly and Munk are growing apart, with Munk focused on learning magic and Jolly's mind on the vow she swore to find Captain Bannon. How will they possibly rely on each other down in the depths, when they are so distant now?Can Soledad, rightful heir to the pirate throne, convince the crews to follow her instead? It will take a duel before they'll even listen to her...This is an epic swashbuckling adventure!