The Blue Pool, McKenzie River, Oregon
It does exist! Janet & I ventured into the heart of the central Cascades to find the mythical Blue Pool. The Blue Pool is part of the upper McKenzie River, and for some reason that could possibly be scientifically explained, is an iridescent blue. From the cliff above, where we were, it looks pretty shallow. But that's a deception due to its clarity - it's about 30' deep! People were cliff jumping from about 50' or so.
The other weird thing about it is that while being part of the McKenzie River (at the bottom of the picture you can see water flowing out) it has no discernible input. About 3 miles upstream the river disappears into the ground, and feeds this pool from below.
Despite a heavily traveled hiking trail in, it's really a magical place,