Brineblood the pirate is back on the high seas with a dastardly plan - he's going to steal every drop of sea magic and use it to raise an all-powerful monster from the bottom of the ocean. If Alex, Zoey and Anil can't stop him, the monster could flood the entire world. Teaming up with the water dragon, they use a home-made submarine to journey deep into places no human has been before. But they have one crucial problem: Alex has lost his magic. Can he still lead his crew to victory? Or will Haven Bay - and the rest of the world - be lost for good?