Find on the picture seven sea urchins, two shells of a Muricidae purple snail (that are presently occupated by hermit crabs, I guess), and a pair of Diplodus seabreams, if six of the urchins sit in breaks, and two are decorated with pompons of alga and seaweed. Shells are equal in size, but one of them is grey and ribbed, though the other is slightly covered with greenish alga. Fishies are almost identical in pose and position on a Y-axis, but different in dimensions.