Geoduck clams are found in the waters of the northeast Pacific from Alaska to Baja California. Living at variable depths from the low intertidal zone to more than 100 metres, they burrow into the ocean floor. A developing geoduck digs about a third of a metre per year. After reaching about a metre depth, the adult geoduck settles in for a long uneventful life.

Geoduck clams are bivalves, and have two shells that are white and somewhat rectangular in shape. Their equal-sized valves do not conceal their enormous siphon (neck), which is white to reddish-brown in colour. Geoduck clams are the largest burrowing clams in the world, with a shell length that can exceed 20 centimetres. They generally weigh between 0.5 and 1.5 kilograms, but, occasionally, grow as large as 3 kilograms. Geoducks are slow-growing and long-lived, with maximum ages of at least 168 years.