Somewhere in this world, there is a temple created by the People of the Water. The Sea Temple contains a hidden treasure, the Sea Crown, but no one has ever seen it because the temple is protected by a secret mechanism. So it drifts through the vast ocean undetected, waiting... waiting...

Ash and Pikachu learn about the legend and meet Jackie, a Pokémon Ranger on a mission to protect a Manaphy egg and find the temple. The Phantom, a nefarious pirate, plans to obtain the Sea Crown and take over the world--but first he needs the Manaphy egg. What is the Sea Crown? How does Manaphy's mysterious power connect it to the Sea Temple? Can Ash help Jackie complete his mission?