The present invention relates to an ultra-sonic device, which can be utilised in an aquatic environment to inhibit growth of waterborne flora and fauna. In particular, the present invention relates to a method of reducing such growth and the removal from the underside of yachts, boats and the like. In general, the present invention relates to anti-fouling systems as are known to prevent biological growth such as algae, seaweed and crustacea on marine vessels or underwater structures. Coating materials have been developed preventing corrosion due to oxidation of the surface of the structure. Although such materials have effects of retarding growth of the corrosion, however, they contain zinc, lead, copper, etc, raising a problem of environmental pollution due to dissolution of these metals into seawater. In addition, none of these coating materials can prevent clinging of marine organisms, and if they cling to the structure, oxidation is accelerated by oxygen sent out from the marine organisms, causing further growth of the corrosion of the structure. The formation of encrustations of barnacles, tunicates, and like fouling organisms, will increase the vessel's weight, thereby decreasing the available storage space, slow a vessel underway, increase its fuel consumption, and make it difficult to handle, thus reducing the vessel's performance and efficiency. The present invention addresses this need wherein the transducer is operable on a cyclic basis.