Shallow sublittoral sediments which support seaweed communities, typically including the kelp Laminaria saccharina, the bootlace weed Chorda filum and various red and brown seaweeds, particularly filamentous types. The generally sheltered nature of these habitats enables the seaweeds to grow on shells and small stones which lie on the sediment surface; some communities develop as loose-lying mats on the sediment surface.