NOTE: If you launch from the same spot all the time, you can put a screw anchor offshore with a buoy attached.
Dear God Almighty you don't want the Corp of Engineers to find out about that :P
The devils with pointy sticks will be on your butt faster than flies on stink.
Oh, I meant "submerged" buoy <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
(Personally, I used an empty [plastic] water bottle ... they think it's floating trash and simply look the other way.)