The filename of this image is "rocky mountains", but it rather looks like Norway to me. Where is it exactly? No source I find through Google Images or through tineye will be more specific than „rocky mountains”.
It's taken in Hamnøy, in the Lofoten island in Norway.
You can even make out the specific mountain shown in your photo in the image included on the Wikipedia page.
To answer the precise question, the lake is called "The Norwegian Sea".
I wish I could say "And I've climbed that". I've done some peaks around Reine (the larger settlement on the west side of the fjord, Hamnøy being the old ferry quay before they built the bridge, and BTW on the right of the photographer, we are looking slightly east of north and behind him/her is only the Lofotfjord), but none of those in the picture. And now I never will, boo hoo.