Abstract: The dredging apparatus includes a vertical hollow body arranged to be lowered to the ocean floor and incorporating a venturi entrance at a bottom opening converging to a throat and thence widening abruptly to define an annular step facing upwardly. The diffusion portion of the venturi extends from the step to the upper part of the body and is defined by a gradually widening or increasing diameter portion. Compressed air or gas is introduced into the throat of the venturi at the annular step by passing the gas through a series of vertical holes or orifices passing through the step. The step results in cavitation of the flow of fluid and debris past the exit end of the throat at the step area to result in a reduced pressure at the step surface to thereby facilitate the flow of gas upwardly through the step. The fluid and debris are passed up to the surface of the ocean by an appropriate conveying means either in the form of flexible hose or a series of pipe sections.