Vivid Blue, Crater Lake, Oregon

Crater Lake is a caldera lake in the western United States, located in south-central Oregon. It is the main feature of Crater Lake National Park and is famous for its deep blue color and water clarity. The lake partly fills a nearly 2,148-foot -deep caldera that was formed around 7,700  years ago  by the collapse of the volcano Mount Mazama. There are no rivers flowing into or out of the lake.  Source