Buoy
BUOY, noun A close empty cask, or a block of wood or cork, fastened by a rope to an anchor, and floating on the water, to show where the anchor is situated. Buoys are of various kinds, as can-buoys, in the form of a cone; nun-buoys, which are large in the middle, and tapering nearly to a point at each end; cable-buoys, empty casks, employed to buoy up the cable, in rocky anchorage. Buoys are used also as marks, to point out the situation of rocks, shoals, or a channel.
To stream the buoy is to let it fall by the ship's side into the water, before letting go the anchor.