Plesiosaur

The sea monster that did Ganzack's bidding. The sea monster was a massive plesiosaur. The monster wore a helmet on its head.

Upon the Strawhats's first encounter with the beast, it kidnapped Nami despite Luffy's attempt to eat it. Later, it assisted Ganzack in his battle against Luffy. The monster was finally defeated by the islanders who hurled dynamite at it, sinking Ganzack's ship in the process.