Abstract: A water pressure operated post-hole digging tool. The tool includes a vertically elongate pipe with an enlarged mandrel member having a generally circular cross section mounted on its lower end, and an attachment for connecting the upper end of the conduit to a source of water pressure. The water pressure is discharged through an open end at the bottom of the mandrel member, so that soil is dislodged at the bottom of the post-hole bore. The flow of water then passes upwardly through the annular cavity around the sides of the mandrel member so as to scour out of the sides of the bore. The lower end of the mandrel member is tapered so as to accelerate the flow of water as this passes into the annular cavity around the body, and upper taper slows the flow as it exits the cavity and flows up the excavated bore. The mandrel member may be formed of solid plastic material.