Thanks for the plug Jdee!
The other thing you can do, if you are just looking for a lake outline (and it sounds like you are, in the OP), is to trace your lake outline in Google Earth. You can then save this polygon/polyline as a KML file, and convert it to a GPX file in something like GPSBabel. Then run it through HBPC to create a track, load it into your unit and set the track style to something solid. You'll then see your lake outline.
matt