Velvet swimming crab. The velvet crab (alternatively velvet swimming crab or devil crab) is the largest swimming crab found in British coastal waters, with a carapace width of up to 100 mm. The body is coated with short hairs, giving the animal a velvety texture, hence the common name. It is one of the major crab species for UK fisheries. The velvet crab lives from southern Norway to Western Sahara in the North Sea and north Atlantic as well as western parts of the Mediterranean Sea, on rocky bottoms from the shoreline to a depth of about 65 m. The last pair of pereiopods are flattened to facilitate swimming. The flesh is succulent and sweet.