Yuda

Yuda (ユーダ, Yuuda) are a ferocious, poisonous type of sea serpents. They live in the Calm Belt and are so dangerous that they are one of the few animals Sea Kings won't attack, but apparently the Kuja people were able to domesticate them. Boa Hancock and her two sisters own a ship which is drawn by these creatures, a newly added method of navigating through the Calm Belt.

Trivia

 * Yuda are the second species that are fiercer than Sea Kings owned by a Shichibukai (Boa Hancock), the first being Bananawani owned by Crocodile. Both of them are also common in being reptiles.