Since day one I have thought the perp(s) arrived by boat and that Mrs. D didn't even make it across the lake before they dumped her overboard (in a robe?...pocket full of rocks?...weighed down by anchor?).
Here is the location of the public boat ramp (Long Shoals) that WSB reported the Sheriff used to exit the lake:
https://maps.google.com/maps?q=Rive...=us&ei=_pF2U4jzNpXLsQTs54LwBA&ved=0CCgQ8gEwAA
This is not (as the crow flies) far from Great Waters, but it was also reported that she was found near the dam (Wallace Dam). It may have been that Long Shoals was just the easiest public ramp for LE to get access to the area.
I know nothing of fluid dynamics, but wonder if a body would follow the (subterranean) river currant to the dam.