This is only a tiny starfish and his colouration made him tricky to spot against the rocks. But I had my niece and nephew with me and I had to show them the beautiful underside of the starfish.
The underside is made up of hundreds of tube feet that allow the starfish to 'walk' and also to prise open shellfish for eating.
Starfish have a kind of armour - outer coating of calcium carbonate (which makes limestone, so it's tougher than a garden snail shell but not as tough as say a hermit crab shell) and tiny spines, which gave this starfish a rough surface.
Starfish aren't fish. They're echinoderms, along with brittle stars, feather stars, sea cucumbers, sea stars, sea urchins and sand dollars.