Satoshi and his comrades become lost in an unfamiliar wasteland, but fate leads them to a "Water Pokemon Show" starring Hiromi, the Mariner Troupe's shining star. Hiromi descends from a lineage of Water People who possess the ability to communicate with water pokemon. She shares an epic tale passed down from her people, revealing the existence of the "Water Temple Akuusha" located in the sea. According to legend, the temple houses a precious treasure known as "The Water Crown," which remains hidden to this day. However, a Pokemon Ranger named Jack Walker, aka Jackie, arrives with the mission of finding it. Jackie is entrusted with protecting the egg of Manaphy, the leader of all water pokemon and known as the "Prince of the Sea." The egg must be transported to the Water Temple Akuusha, and Satoshi, Hiromi, and Jackie team up to ensure its safe arrival. Their journey is met with trouble as the pirate Phantom and his massive submarine attack them. Phantom desires the Water Crown's power to establish himself as an earth-dominating force. But first, he must crack the puzzle of Manaphy's egg. Team Rocket's Jessie, James, and Meowth jump into the fray, only for Jackie to use his Capture Styler to harness nearby pokemon's energy and foil their plans. Satoshi and Pikachu also join the battle, only to face off against Phantom's advanced mecha. During the chaos, the egg emits a brilliant light, signaling the birth of Manaphy! What secrets lay in Manaphy's unique abilities? And what is the truth behind the mysterious Water Crown? Satoshi and his allies continue their quest to locate the Water Temple Akuusha, their adventure only just beginning.