Gorgeous lake and a great back country portal. If you are good with a map and compass you can go off trail from here all the way up to Cloud's rest and bivy there for some of the most amazing views of Yosemite with no one else around.
Park at the turnout that says "sunset" and walk 3 mins to the south end of the lake where the granite slabs form a natural sloping shore into the lake. There was a campground here that was closed and reclaimed in the 70's. Best quick swim in the whole park IMO.