Closely related to a smaller species found in shallower waters this large form of the Dahlia Anemone, Urticina eques, exists in a huge range of gaudy colours. It can be as much as 20cms across and will envelop just about anything that its sticky, stinging tentacles come into contact with - crabs, sea urchins, prawns, fish all make a welcome meal. See the mouth parts on the next photograph. Whilst digesting its food, the anemone draws its tentacles into its stem and basically shuts down, looking like an unattractive lump of dense jelly.
St. Abbs Marine Reserve, Berwickshire. E. Scotland