Limpet (Patella vulgata).
Very common on rocky shores around the coast of Britain.
The limpet is one of the easiest animals to spot on the rocky shore. It is a snail-like creature that lives inside a tough, cone shaped shell like a round, pointed hat. The shell grows to about 3cm high and 6cm in diameter.
The limpet sticks itself very tightly to rocks on the seashore to protect itself from drying out, from being washed away and from being eaten by predators such as the oystercatcher or dog whelk.
Limpets do not stay in the same place all the time. When the tide comes in, limpets need to find food. They move around slowly on a muscular foot like a snail, scraping algae and young seaweed off the surface of rocks using a rough sort of tongue called a radula.
When the tide goes out the limpet is in danger of drying out in the air, so it returns to the exact spot where it was sitting before and sticks itself to the rock. It leaves a tiny gap around the edge of the shell, big enough to let oxygen in so it can breathe, but not big enough to let water escape.
Limpets often wear away a patch on the rock where they sit which fits the shape of their shell exactly. This patch is called the home scar and you can often find these on rocks where limpets have been living.
It is important not to try to remove a limpet from its patch on the rock. If it can't find its way back to its home scar it will probably die.