Abstract: A method and apparatus for determining the surface level of a given body using acoustic ranging that incorporates processes natural to human beings to improve identification of the echo from the water surface when spurious echoes might otherwise overshadow it. An acoustic beam is transmitted toward the surface where it is reflected. The beam also reflects off various interferences creating spurious reflections or echoes. The echoes from the surface as well as the spurious echoes are then received. Each echo is then evaluated according to several criteria, in order to determine which echo is associated with the surface.