Abstract: An anchor device adapted to be buried in a bed of material and including an anchor head comprising a generally hollow cylindrical body having an upper portion adapted to be releasably secured to a hollow placement stem connected to a supply of fluid under pressure. A lower portion of the anchor head has a tapered nose and at least one downwardly oriented jet aperture is provided in the lower end of the nose and a plurality of upwardly-angled jet apertures are provided in the walls of the nose for transmitting fluid into the bed material surrounding the nose to fluidize the material and drive the head into the bed. A fin assembly is mounted on the anchor head intermediate the top and bottom portions and comprises a plurality of fins and a collar and bracket arrangement for mounting a foot portion of each of the fins for rotation between a folded position generally parallel to the axis of the anchor head and an unfolded position at a substantial acute angle to the axis.