Lake Chelan, Washington. I have been here personally during the summer and this place is beautiful! You can go paddle boarding, kayaking, etc. The water is clear and perfect temp! I definitely recommend visiting or camping there!
The resort is called Dunton Hot Springs and it’s in Colorado. It’s an incredible little ghost town in an alpine alley with mountain views and a waterfall. Best of all it features historic cabins to stay in–some tiny and others quite large.