Two state parks provide camping and other attractions along the south shore of Lake Chelan [1]. Lake Chelan State Park is right on the lake, nine miles west of Chelan [2], with an underwater park, a boat launch, and concession stand.
Twenty-Five Mile Creek State Park (20530 S Lakeshore Rd., www.parks.wa.gov [3]) has a swimming pool for campers and a boat launch.
Links:
[1] http://www.moon.com/destinations/washington/north-cascades/chelan/sights/lake-chelan
[2] http://www.moon.com/destinations/washington/north-cascades/chelan
[3] http://www.parks.wa.gov