ONE PIECE: UMI NO HESO NO DAIBOUKEN-HEN

The Straw Hats encounter a city in the middle of a whirlpool, called the Ocean's Navel, that is being destroyed by giant monsters. These monsters supposedly protect a treasure capable of granting wishes, but in the process of defeating these guardians, the crew ends up releasing another evil. (aired after Episode 53) — Description from AniList community (anilist.co).