One Piece: Umi no Heso no Daibouken-hen

(Esta sinopse está em inglês. Ajude a comunidade traduzindo!)

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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)

(Source: Wikipedia)