Pokémon Ranger and the Temple of the Sea

Original: 劇場版ポケットモンスター アドバンスジェネレーション ポケモンレンジャーと蒼海の王子 マナフィ

On their way through the Battle Frontier, Ash and friends meet up with a Pokémon Ranger who's mission is to deliever the egg of Manaphy to a temple on the ocean's floor. However, a greedy pirate wants the power of Manaphy to himself.