Some bivalves move around the sea freely, while others prefer a sedentary life. Bivalves use gills on each side of their mantle to filter nutritious micro-organisms from the surrounding water.

Mussels grow clustered in dense beds on rocky shorelines. They anchor themselves with strong threads known as byssus. Other species such as the golden oyster become cemented to rocks or coral, using the flatter shell in the pair as a base.

Like many bivalves, cockles are able to shut their shells, with interlocking teeth and notched edges providing a secure seal.