The cockle is a filtering bivalve mollusc that lives buried at a depth of about 5 centimetres in sand or mud, where it feeds by filtering the phytoplankton from the water. When threatened, it can quickly burrow deeper by the retraction of the foot that keeps it anchored, which manoeuvre sometimes sallows cockles to escape predators. Cockles are very common and up to 10,000 animals per square meter can be found. Because of its high tolerance to low salinity environments, it is also frequently found in estuaries.