Pokemon the Series: Ruby & Sapphire Season 603 Episode 6 Abandon Ship!

Ash and friends foil a Team Rocket kidnapping scheme on the high seas, but are then left high and dry themselves when Team Rocket's boat breaks down. Drifting with the tide, they eventually come to rest against an abandoned ship. On board, they meet one of the ship's original passengers, Tommy, who has returned to search for the Marshtomp he was separated from when the ship first ran aground. Happy to have found a ride back to land, Ash and friends offer to help this passenger in his search. As the group moves below deck, however, their party begins disappearing, one member at a time. The shadowy figure responsible turns out to be a Swampert, which evolved from Tommy's Marshtomp! The two are reunited, and our heroes are released. Tommy sees that the ship has become a haven for Water-type Pokemon, and stays on board with Swampert to fix it up into the best home it can be.