large fluffy anemone with thousands of small tentacles
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This species is ridiculously common in the Menai Straits, near Bangor where I was university - at least it was in the 1970's. If you can't go diving like Trudy try looking over the edge of any old wooden pier at spring low tide. In most parts of the coast you will see these beautiful beasts just under the water studding the vertical posts.
Lat/Lng: 50.1, -5.0
OS grid ref: SW9236