Occurs on extremely wave-exposed to exposed circalittoral bedrock and boulders subject to tidal streams ranging from strong to very strong. Typically found in tidal straits and narrows. The high energy levels found within this habitat complex are reflected in the fauna recorded. Sponges such as Pachymatisma johnstonia, Halichondria panicea, Esperiopsis fucorum and Myxilla incrustans may all be recorded. Characteristic of this habitat complex is the dense 'carpet' of the hydroid Tubularia indivisa. The barnacle Balanus crenatus is recorded in high abundance on the rocky substrata. On rocky outcrops, Alcyonium digitatum is often present.