One Piece: Gyojin Tou-hen

In the journey to get the One PieceLuffy and his friends have to pass from Fish-Man- Island. This island is under the control of fishermen and mermaids. They rampage in the human village and rob them every time. It is a submerged kingdom that is located across the red line. Luffy and his friends when passed from that island. They decided to set them free from the Fishmen. The leader of them is Hody Jones a radical Fish man. They fight against them and win the battle and are finally able to set free all the humans there.