I moor my Hobie 18 to a 9" inflatable buoy chained to a 3' galvanized steel anchor (a huricane tie-down) augored into the river bed (and coquina rock below). You may want a larger anchor with 6" diameter heilicoil if you're just going into sand.
The key is to minimize damage due to the constant motion of the boat. In addition to things Sailing a Ray and other bring up, I would ensure that you attach a large snap ring from the buoy to the dolphin striker down rod. This prevents the buoy from rubbing up against your gelcoat.
You also need to keep slack in the chain or rope for changes in tides/waves. Yet you don't want too much that it causes your boat to get yanked if the wind does a 180! I use bungie cords from the anchor head to the bottom of the buoy.