Winter flounder have an oval shape and a thick body with a tiny mouth. Their eyes are on the right side of their body and widely spaced. They have a straight lateral line and dark coloring. Their coloring often varies with their habitat, ranging from muddy to slightly reddish brown, olive green, or dark slate, to an almost black upper. Their underside is white, and their dorsal and anal fins are often tinged with pink, red, or yellow.