Device for positioning a buoy body, comprising a ballast weight which in use is positioned under the buoy body and is provided with anchors, and a coupling connecting the ballast weight to the buoy body. The greatest horizontal cross sectional dimension of the buoy body is substantially less than the height of the buoy body. The buoy is spaced a substantial distance from the ballast weight. An elongated tubular member is secured to and extends upwardly from the ballast weight, the buoy body surrounding only the upper end of this tubular member. Swivel bearings interconnect the tubular member and the buoy body for relative rotation about an upright axis.