Mohmoo is a giant "sea cow" that was brought from the Grand Line by Arlong's crew. This creature was responsible for destroying Gosa Village. However, when it encountered Luffy, Sanji, and Yosaku's boat, it was quickly defeated and subsequently used to tow their boat to the island. Later, during the battle at Arlong Park, Hatchan, who acts as Mohmoo's caregiver, summoned it to fight the Straw Hats. Despite recalling its previous defeat, Mohmoo obeyed but ended up being utilized in Luffy's Gomu Gomu no Kazaguruma attack, which took out most of Arlong's forces. It was then thrown out of Arlong Park, never to be seen again. Mohmoo is possibly an ophitauros.
It can produce a "moo" sound like any typical cow. Interestingly, it seems to have no trouble staying on land, as Arlong's crew dragged it through Gosa Village without it sustaining any known damage.
First Appearance: Chapter 73; Episode 31
