The shanny has a smooth, elongated body, and measures up to 16 cm in length. Its colouration varies with surrounding habitat from dark brown or blotched to blackish, with a dark spot behind the first dorsal fin. The blennies in general have an elongated body with a large, blunt head, fairly large eyes, and small tentacles on the head. The shanny has similar characteristics to other blennies, although it has no head tentacles and its eyes are set high up on its head. Older animals develop a fleshy ridge on their forehead.