Cockles are a type of saltwater clam that live buried a few centimetres under the sand in tidal zones. They are known as bivalve molluscs and have two small tubes that stick out above the sand. The cockles use these tubes to filter water and plankton but they can also distinguish between light and dark. Different factors influence the growth of cockles including the salinity and temperature of the water. The current cockle fishing industry is restricted and only hand-picking is permitted.