It is a cephalopod. They have a highly muscled mantle, eight arms or tentacles endowed with two rows of suckers. They can be orange, brown or yellow and they use their vast colour changing ability either to camouflage or to reflect their emotional state. This species can reach up to 40 cm (6 in) mantle length and a total length of 1,6 m (5 ft). It feeds mainly on fish, small crustaceans and bivalves.

Octopi have three hearts: two branchial hearts pump blood through each of the two gills, while the third is a systemic heart that pumps blood through the body. Cephalopods such as octopi, cuttlefish and squids have blue blood because they use a copper-based transporter protein called hemocyanin instead of hemoglobin wich contains iron. The copper in hemocyanin makes their blood run blue.

It can perfectly blend into its surroundings by changing not only the colour but also the texture, with the ability to transform itself into the shapes of many others species found in the sea. However, they will automatically change its colour when they are mating or feel threatened. It is one of the most exploited commercial species and can be found along the Andalusian coast.