Abstract: A system for entrenching an underwater pipeline on a water bottom. The system is comprised of an underwater pipeline positioned on a water bottom; a floating vessel; an elongated tubular entrenching tool having a plurality of tool nozzles; a jetting head having a plurality of nozzles attached to the entrenching tool by a flexible jetting head hose; first and second waterlines; means for connecting the first waterline to the rear end of the entrenching tool and means for connecting the second waterline to the front end of said tool; and means for suspending the entrenching tool below the pipeline. A pump supported on the surface vessel is connected to the waterlines and is utilized to pump a volume of water at a desired pressure through the waterlines to the entrenching tool to create a trench on the water bottom for entrenching the pipeline by the jets of water at the tool and jetting head nozzles.