Kuroobi is a raytype fishman. Kuroobi is one of the strictest members in his crew and has always been wary of Namis supposed allegiance to Arlong. Kuroobi practices FishMan Karate called Merman Karate in the now defunct 4kids dub to fight his opponents. During the battle with the Straw Hats in the Arlong arc he fights against Sanji whom he nearly defeats when the cook goes underwater to try and save Luffy. As a FishMan Kuroobi has an advantage underwater. However Sanji manages to force him up to dry land by breathing the air from his gills suffocating him and then promptly beats him into submission with his kicks. Source: Wikipedia