The ‘Submerged or partially submerged sea caves’ habitat is listed on Annex I of the EC Habitats and Birds Directive. Caves conforming to this habitat type can be found distributed around the rocky stretches of Welsh coastline from Gower to Anglesey. The partially submerged caves, some of which are accessible on low spring tides, are subject to strong wave surges and characterised by communities of mussels, barnacles, cushion sponges, encrusting bryozoans and colonial ascidians.