Despite its name, the great shipworm is not a worm. It is a bivalve with incredibly small shells on an elongated, unprotected mollusc body. It lives together with bacteria that can digest wood. In that way, it is able to 'eat' wood while digging a protective tunnel at the same time. The wooden ships in the 17th century brought the animal to the Netherlands. In the 18th century, the animal created a huge disaster. It destroyed all the wooden piling used to protect the dikes. Nowadays, the great ship worm still forms a threat for the ship wrecks in the Wadden Sea.