Wave-sheltered, mainly upper and mid shore flats of medium to fine sand, often muddy sand. The salinity, although predominantly recorded as variable, probably varies little from fully marine in these broad estuaries. The infauna is characterised by the amphipods Bathyporeia pilosa, Corophium arenarium and C. volutator, and the spire shell Hydrobia ulvae. Polychaetes and bivalves are limited in their abundance and variety, though the Baltic tellin Macoma balthica may occur. Tidal streams may be strong during spring tides, accounting for the presence of amphipods B. pilosa that are more commonly associated with open coast sandflats. Situation: This biotope is typically found higher up the shore than sandflats with the cockle Cerastoderma edule (unit A2.242) in the large sandy estuaries of the west coast of England and Wales. In moderately exposed conditions, can occur on the mid shore below units A2.211and/or A2.221. In more sheltered conditions, may occur above unit A2.311.