Abstract: 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.