The main body mass is enclosed in the mantle, which has a swimming fin along each side. These fins, unlike in other marine organisms, are not the main source of locomotion in most species. The skin is covered in chromatophores, which enable the squid to change color to suit its surroundings, making it practically invisible. The underside is also almost always lighter than the topside, to provide camouflage from both prey and predator.
The majority are no more than 60 cm (24 in) long, although the giant squid may reach 13 meters (43 ft).
In English-speaking countries, squid as food is often marketed using the Italian word calamari. Squid are found abundantly in certain areas, and provide large catches for fisheries. The body can be stuffed whole, cut into flat pieces, or sliced into rings. The arms, tentacles, and ink are also edible; in fact, the only parts not eaten are the beak and gladius (pen). Squid is a good food source for zinc and manganese, and high in copper, selenium, vitamin B12, and riboflavin.