Anchor bouys are one of those nifty things that are nodded over and not nearly asked enough about.
One some of the fancier capital ships, in peacetime, the bouys were sometimes painted half red, and half green, to match the starboard and port designation colors.
You put buoys on the anchors, as anchors are expensive things, as are the cable hawsers bent to them. If an emergency beckoned, you slipped the cable (one does not casually chop though a 36' cable except in dire extremis). Since the rode was put out at 1:7, the buoy line was relatiely short, and gave a good indication of where the crown was, under the waters.
Once the extremity was passed, you could sail over to the buoy and clap on tackle to it, and hoist away. Because the buoy line was bent on the crown of the anchor, hoisting that line would pluck the "sunk" fluke out of the bottom neatly.
On a rocky bottom, sometime the buoy line would be used to wrest the anchor loose of the rocks, rathet than just using brute force heaving away at the rode.
Our dafi detailied up a very nice buoy for his recent partial side of Victory. Durst if I can find the thread to link it, though