May gets a proper goodbye, and the movie knows it, every scene with Manaphy hits because you understand what she's actually losing. The underwater sequences build from spectacle into genuine stakes, the kind where you stop thinking about it being a kids' movie. A Pokémon Ranger shows up and undercuts the mood constantly, which drags everything down, but the bond between May and that mythical creature is the one thing this film refuses to let you forget.

Lost in an unfamiliar wasteland, Satoshi and his friends come upon a water Pokemon show starring Hiromi of the Mariner Troupe. She descends from the Water People, who could talk with water Pokemon, and she tells them a legend her people have handed down: an ocean temple called Akuusha hides a treasure known as the Water Crown. A Pokemon Ranger named Jackie then appears on a secret mission to guard the egg of Manaphy, the Prince of the Sea, which must be brought to the temple. Satoshi's group and Hiromi agree to help, but the pirate Phantom attacks from his submarine, hoping to use the Crown to rule the world, and the Rocket-Dan join the fray.