From Bulbapedia, the community-driven Pokémon encyclopedia.
Bluefinland (Japanese: ツナタウン Tuna Town) is an anime-exclusive location in Johto. It is a northern port town on Blue Point Isle that runs a ferry to Yellow Rock Isle.
Ash and his friends wanted to get to Bluefinland in Takin' it on the Chinchou. However, they accidentally ended up in another town called Blue Lagoon. After Ash and his friends saved a group of Chinchou from Team Rocket, the group now traveled to Bluefinland and took the ferry to Yellow Rock Isle. When the boat left, Misty spotted a Corsola on the docks of Bluefinland, much to her delight.
Pokémon seen on Bluefinland
Bluefinland is probably a reference to Finland, a country in Northern Europe. It may also come from Bluefin, which is a species of tuna. Furthermore, it could be a pun on Newfoundland, an island that makes up the Canadian province Newfoundland and Labrador.