My Wildlife of the National Trust is limited to animals, but is this an animal or a plant? the answer seems to be 'both' but I won't go into the technicalities and genetics. This little thing is the bright red blob you will see in rock pools when the tide goes out (as in the second photo). However, when the tide comes in, the Beadlet Anemone opens out, and extends its tentacles, which sting its prey of crabs, shrimps, small fish. as well as the red colouration, they have bright blue beads at the base of the tentacles (but I've not managed to capture this in a photo...)