The Site is an extensive shoal area lying 34 kilometres south of the Channel Island of Jersey. It supports over 40 different biotope types, and around 600 marine species have been recorded. There are extensive kelp forests and subtidal seagrass beds. Shallow waters and intertidal pools provide habitat and act as a nursery area to a wide range of fish and invertebrates, including species of commercial interest such as crabs and lobsters. The cold-water reef is characterized by species at the northern or southern limit of their ranges. Some species are regionally scarce, or globally vulnerable such as the green ormer (Haliotis tuberculata) and pink sea fan (Eunicella verrucosa). The Site supports a small breeding population of grey seal (Halichoerus grypus) and one of the largest breeding populations of bottlenose dolphin (Tursiops truncates) in the British Isles. It also provides feeding and roosting locations for passage and wintering waders and wildfowl, and there are several notable nesting bird colonies. The area is frequently used for recreational fishing, especially potting, low-water fishing and angling, and supports an important commercial fishery for various mixed shellfish and wet fish. The main threats are posed by dredging; over-fishing and harvesting of other aquatic resources; erosion and disturbance of breeding bird species from recreation and tourism; invasive non-native species; and climate change.