This habitat feature consists of soft sediment types that are permanently covered by shallow sea water (generally less than 20m deep).

The diversity and types of community associated with this habitat type varies according to sediment type, geographical location, exposure of the coast and the depth, turbidity and salinity of the surrounding water. There are several major sandbanks within the SAC, including Bais Bank, Turbot Bank, sandbanks in the vicinity of Skokholm (Wild Goose Race and The Knoll), and sandbanks associated with Grassholm Island. There are also deeper sandbanks associated with the Bishops & Clerks, Hats & Barrels and St Govan’s Shoals reefs and in the north-west and south-west of St Bride’s Bay.

Each sandbank is unique and has its own characteristic communities. Shallow sandy sediments are typically colonised by burrowing animals such as worms, crustaceans, bivalve molluscs, and echinoderms (starfish and urchins). Prawns, crabs, snails and fish (such as sand eels - an important food for birds) may live on the surface. These banks can be important nursery areas for fish and feeding grounds for seabirds. The deeper more stable sandbanks tend to be richer in species than the more mobile, exposed and shallow sandbanks.

Turbot Bank, to the south-west of the entrance to the Milford Haven waterway, is roughly ovoid in shape and influenced by complex tidal stream patterns. Dunes, waves and ripples are important sandbank micro-niches which increase habitat and community diversity. The fine-medium sand here tends to show an increased species richness with depth, with possible seasonal variability.