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Scoured rock in wave-surged caves, tunnels or gullies often looks rather bare, and may be characterised by a limited scour-tolerant fauna of Balanus crenatus and/or Spirobranchus triqueter with spirorbid polychaetes. In areas where sufficient light is available and scour is severe, encrusting coralline algae and non-calcareous crusts cover the rock surface, giving a pink appearance. This biotope most commonly occurs at the bottom of walls in caves and gullies, where abrasion by cobbles and stones is severe, especially during winter. In some gullies, extreme scouring and abrasion produces a narrow band of bare coralline algal crust at the very bottom of the walls, with a band of P. triqueter and/or B. crenatus immediately above. Other scour-tolerant species, such as encrusting bryozoans may also be common. Crevices and cracks in the rock provide a refuge for sponge crusts such as Halichondria panicea and occasional anemones Urticina felina and Cylista elegans. More mobile fauna is usually restricted to the echinoderms Asterias rubens and Echinus esculentus as well as the crab Cancer pagurus. Two variants have been identified: Wave-surged bedrock with coralline crust, B. crenatus and P. triqueter (CC.BalPom) and coralline crusts on mobile boulders in severely scoured caves (CC.Mo).

Highly mobile and scoured boulders and cobbles found on cave and gully floors and which often appear bare. Where there is sufficient light and stability, however, the boulders are encrusted by coralline algal crusts. Barnacles Balanus crenatus and keelworms Spirobranchus triqueter may survive in areas protected from severe abrasion. Crabs such as Cancer pagurus and Carcinus maenas may occur, often beneath and between the rocks, along with the gastropod Calliostoma zizyphinum. The anemone Actinia equina may be present in low numbers.

Severely scoured bedrock in wave-surged caves, tunnels or gullies often looks rather bare, and may be characterised by a limited scour-tolerant fauna of Balanus crenatus and/or Spirobranchus triqueter with spirorbid polychaetes. In areas where sufficient light is available, encrusting coralline algae and non-calcareous crusts cover the rock surface, giving a pink appearance. This biotope most commonly occurs at the bottom of walls in caves and gullies, where abrasion by cobbles and stones is severe, especially during winter. In some gullies, extreme scouring and abrasion produces a narrow band of bare coralline algal crust at the very bottom of the walls, with a band of P. triqueter and or B. crenatus immediately above. In some caves extreme wave surge at the back of the cave leads to a zone of this biotope which may also be dominated solely by sprorbids or by the barnacle Verruca stroemia. Other scour-tolerant species, such as encrusting bryozoans may also be common. Crevices and cracks in the rock provide a refuge for sponge crusts, small Mytilus edulis and occasional Actinia equina, Urticina felina and Cylista elegans. More mobile fauna is usually restricted to the echinoderm Asterias rubens and the crab Cancer pagurus. During periods of relative stability in the summer, small quantities of foliose red seaweeds and opportunistic kelps may occur where sufficient light is available; the seaweeds however do not dominate (compare with FoSwCC).