Abstract: The invention generally pertains to apparatus for determining bedload thickness of a bedload on a bed surface in an aquatic medium. An acoustic source is operative when energized for producing incident acoustic waves in the medium directed at the bed surface resulting in reflected waves. An acoustic sensor is movably locatable between the acoustic source and the bed surface and is responsive to the incident and reflected waves for producing a variable output representative of the sum of the incident and reflected waves. The sum varies between a maximum and a minimum with distance from the bed surface. A height sensor is responsive to the position of the acoustic sensor relative to the bedload thickness for producing an output indicative thereof. A processor responsive to the acoustic sensor output and the height sensor output produces an output indicative of the thickness of the bedload thickness.