The Site consists of two small islands (Herm and Jethou), nine rocky islets (inlcuding Grande Fauconniere Crevichon, Brehon Tower and The Humps), and the surrounding shallow tidal waters, near the larger Channel Island of Guernsey. It is located within the Normand-Breton Gulf, a large marine area in the western part of the English Channel that includes numerous marine protected areas with six marine Ramsar Sites as well as European Union Natura 2000 sites and areas with national French designations. The Site is rich in biodiversity, with the intertidal zone being particularly large and biodiverse. Its important habitats include eelgrass (Zostera) beds, shallow reef systems and sunken shipwreck reefs that provide spawning grounds and nursery areas for many species of fish and invertebrates, such as European sea bass (Dicentrarchus labrax) and Atlantic mackerel (Scomber scombrus). Globally threatened species include the green ormer (Haliotis tuberculata) and the critically endangered Balearic shearwater (Puffinus mauretanicus). Several marine mammals frequent or are resident within the Site, including Atlantic grey seal (Halichoerus grypus), bottlenose, common and Risso’s dolphins (Tursiops truncates, Delphinus delphis and Grampus griseus) and harbour porpoise (Phocoena phocaena). The commercial and recreational fishing opportunities within the site are of high cultural and economic importance to the population of Guernsey. There are significant archaeological and historical features, and part of the Site is a tourist destination used for a variety of recreational and educational activities.