Abstract: Active sonar systems are usually used to locate objects in mid-water, while passive systems are used to determine the range and direction of sources of sound Some systems can yield information about the seabed, for example a depth sounder can give a plot of depth along the travel direction, while a side scan sonar can give a two-dimensional image of the sea bed This paper describes the application of a parametric sonar system that can generate a narrow beam with enough acoustic power to penetrate the water/sea bed interface. Subsequent acoustic scattering at deeper interfaces may yield information about the underlying sediments or the detection and ultimately the characterisation of buried objects such as lost cargo, mines, pipelines or shipwrecks.