Cockle is the name of a common group of clams. Cockles have a hard, protective shell consisting of two pieces called valves. The valves are round and have deep grooves. There are about 200 kinds of cockles worldwide. Most live in shallow ocean waters, but some occur as deep as 1,000 feet (300 meters). Cockles move about by using a long, muscular organ called a foot. The foot can flip a cockle short distances or help it burrow beneath the sandy ocean bottom. Cockles range from about 1/3 to 8 inches (1 to 20 centimeters) in diameter.
