The Sea Animal Pirates seem to possess a sufficient amount of strength, as they successfully made it to the New World. The captain also possesses Busoshoku Haki.
After being defeated and inspired by Luffy at Alabasta, one of the Kung-Fu Dugong set sail and formed a crew of only sea animals. When they reached the New World the crew met Breed, who used his power to enslave them.
Caesar Retrieval Arc
Following Breed's orders, the kung-fu dugong and his sea lapahns kidnap Caesar Clown from the Straw Hat Pirates, forcing them and Law to chase the animals in order to recover the scientist. Later Luffy and the Dugong have a short fight and then recognize each other. Breed then appears and orders Luffy and Law to fight. After the dugong protests, Breed instead orders him to throw Law and Luffy into the sea.
Sea Animal Pirates (under Breed's control) vs. Straw Hat Pirates