do not EVER use a shoreline anywhere but the sea.

in real life, there is no shoreline except at the sea. onyl if the wind blows really hard, you have a little shoreline. a wild river of course has one aswell, but a lake never has a shoreline, especially not such a huge one...

check this out:
http://images.google.at/images?hl=de&q=mountain+lake&btnG=Bilder-Suche&gbv=2