Barnacles are some of the most common sea creatures living between high and low water on rocky coasts. The larva of the barnacle can swim freely in the sea, but when it changes into an adult it fixes itself to a rock and then begins to make a shell. It never moves from the place it has chosen.

Barnacles are hiding deep within their shells at low water, giving the impression the shells are empty, but at high water they send out a feathery-looking leg and use it to catch the many tiny creatures floating in the water.

They have a shell made of six plates. They have two further plates inside which they slide across when the tide goes out.

Barnacles are food for whelks. The whelks grind the shells down and then eat the animal inside. Starfish can do much the same. But the huge numbers of barnacles mean they can survive despite this.