In late fall 1730, a coastal flood hit the Dutch island Walcheren. Inside the broken wooden revetments strewn across its beaches, dike authorities noticed peculiar, tiny holes. These holes contained shipworms (Teredo navalis), a marine mollusk that bored into the wooden infrastructure that protected coastal dikes. This discovery prompted the most significant redevelopment and rebuilding of coastal flood defenses in the early-modern period. This chapter investigates the origins, interpretation, and response to the ‘shipworm epidemic’ of the 1730s. It argues that the perception of shipworm novelty influenced this dramatic change. In contrast to epizootics or coastal floods, the cultural memory of disaster presented no ready solutions for shipworms. Shipworms’ perceived novelty catalyzed new natural historical investigations of the species as well as innovative new dike designs. Shipworms also produced new connections to decline. Pietist ministers and enlightened spectatorial journalists united in their condemnation of the moral decay of the Dutch Republic by linking shipworms to an ongoing wave of sodomy trials. The biological novelty of the shipworms translated to an unprecedented period of persecution.