Namur is the commander of the 8th division of the Whitebeard Pirates.

He appears to be some kind of shark-type Fishman, with shark-like teeth and gills. He appears to be a tiger shark Fishman because of the stripes on both sides of his face. He also has a scar or a mark in the shape of a lightning bolt on the left side of his face and fangs protruding from his bottom, similar to Jimbei. He is somewhat short and rotund in shape, and his hair is arranged in spikes pointing upwards, similarly to Foxy. He has the number "8" tattooed to the left of his neck to represent the division that he leads. He also wears a white T-shirt with sky blue sleeves with the star logo for the Criminal brand (colored orange) on the chest. Due to his legs not being visible in the manga, in the anime he was given standard grey pants held up by a belt. In the anime, he is also seen with a gray shark fin protruding from his back, and no shoes.

(source: onepiece.wikia.com)