Protective resemblance is exhibited by some Nudibranch Gastropods which have assumed the colour and appearance of their habitat.
Field Studies Council Publications Can anybody identify this nudibranch found in the seas off Scotland?
She had found a nudibranch on the hull of this huge wreck.
One shot could be of a small nudibranch, the next of an edible crab.
Scottish nudibranchs Great photos of many UK nudibranch species plus link to other nudibranch information.