I found a location from the movie. This where they were putting the canoes in the water and where Dean pushed Whitney out of a canoe. It's also where Nelson attacks Drew at the end. You can see the red building, which is where Nelson emerged from before attacking Drew. The docks are long gone, but this is definitely the spot. This is at Bluff Lake in California. In the commentary, director Ralph Portillo states that they filmed at two camps (one being on Bluff Lake). And there actually is a small summer camp just out of frame.