"This is Flathead Lake in northwestern Montana, USA. The water is so transparent that it seems that this is a quite shallow lake. In fact, it is 370.7 feet deep." "It is one of the cleanest in the populated world for its size and type. Its known maximum depth is 370.7 ft (113.0 m), making it deeper than the average depths of the Yellow Sea or the Persian Gulf." I've been here and it truly is that clear. So beautiful!