Captain Marius is a character of the day who appeared in Around the Whirlpool (EP212). Marius is a captain and fisherman who appears weathered from years on the sea.

He piloted his ship and escorted Professor Elm during his expedition through the Whirl Islands. His vast technical and navigation experience of the area also proved invaluable. Elm holds him in high esteem, though Marius is particularly modest and prefers to not brag about his accomplishments.

During the trip, Marius's boat helped rescue Ash and his friends after they had been blasted off their ferry by Team Rocket. Marius later docked his vessel at the Inland City ports to allow the kids to continue on their own journey through the Whirl Islands. He is deeply interested in Pokémon. He asked Brock about all of the gang's goals and dreams, and admired all of them deeply. Marius freely offers advice and before the group left for their next destination, he reminded them to enjoy the journeys towards their individual goals.