A good anchor that holds, is a chain style anchor. Take 'bout 30+ feet of heavy chain. and make a series of 1 foot loops. Take a 3 foot piece of cable and thread it through one side of the loops and cinch the wire tight. The anchor weighs about 40-50 lbs(if you use the heavy chain. TO make the anchor quiet, wrap the individual loops with duct tape. You end up with a dread-lock lookin' 40+ lb blob, that usually sticks right away.