A glance beneath a starfish reveals hundreds of aptly named tube feet. These are operated by a unique hydraulic arrangement, rather like the braking system of a car, and are used to move the starfish around and handle prey. In most species, the tube feet have tiny suckers at their tips but, in some sand-dwelling starfish, they are pointed and act as spikes.

The sea is full of odd creatures, but few are stranger than the starfish. Those found in UK waters come in a great variety of colours and sizes, ranging from the spiny starfish, which can reach an awesome 80cm across, to tiny cushion stars. Most have five arms but the purple sunstar comes equipped with nine or more.

Any piece of starfish that has a portion of the central body attached can develop into a whole new individual. This is why you sometimes see a starfish comprising one large arm and four tiny ones. Owners of mussel beds would once chop starfish in half before tossing them back in the sea, failing to realise that they were doubling the population!

Many starfish feed on molluscs with two halves to their shell, such as clams and mussels. By hunching over their prey, the starfish can maximise the number of tube feet attempting to prise the shell apart. A force equivalent to 5kg can be created in this way and, eventually, the luckless mollusc will be able to resist no longer.

A starfish needs only to open up the tiniest chink in the armour of its prey. A gap between the shell halves of around one-tenth of a millimetre enables the starfish to slip its inside-out stomach into the molluscs soft centre. The shellfish meal is then digested alive, and opens more and more.

Ever wondered why the surfaces of slow-moving starfish are so clean, unsullied by the likes of encrusting barnacles Their upper surfaces are covered with pedicellariae, structures with tiny plier-like jaws that crush any settling larvae. They might even provide the starfish with a little extra nutrition, too.