Abstract: An antifouling composition that comprises an effective amount of a furanone of the structure shown and a suitable carrier therefor. In the figure, substituents R.sub.1, R.sub.2 and R.sub.3 are each a hydrogen atom, a hydroxyl group, an alkyl group containing from 1 to 10 carbon atoms, an ether group containing from 1 to 10 carbon atoms, an ester group containing from 1 to 10 carbon atoms or a halogenated alkene containing from 1 to 10 carbon atoms or R.sub.2 and R.sub.3 together may comprise an unsubstituted or a halogenated alkene containing from 1 to 10 carbon atoms and R.sub.4 is a hydrogen or halogen atom, and a suitable carrier therefor.