Sea Urchins are usually spherical in shape with a flattened top and bottom. They have close-fitting plates covered with a delicate living skin. The plates bear movable spines. The animal walks aided by its retractable tube feet. The suckers on the end of the tube feet also help the animal to turn itself over and hold onto the rocks during heavy wave action.
See below a short clip of a soft spined sea urchin hiding in some neptune’s necklace.
Video by Carly Spicer.