Professor Imberger has made major contributions to a wide variety of problems in environmental fluid dynamics. His papers on selective withdrawal, natural convection, surface layer dynamics and mixing in stratified fluids are particularly important and frequently cited. His effectiveness arises from an unusual ability to combine advanced mathematics and statistics, laboratory modelling and pioneering sophisticated techniques of field instrumentation. Professor Imberger has been directly responsible for the creation of associated organizations which together constitute one of the strongest groups in environmental fluid dynamics anywhere in the world. He and his colleagues are widely consulted on diverse environmental engineering problems both in Australia and overseas.