The blue of Crater Lake is indescribable and unforgettable. It's a color you've never seen before. Cameras can't capture it, and memories don't prepare you to see it again... they don't truly capture it, either. In terms of the physics of the situation, I understand how Rayleigh scattering in exceptionally pure and deep water returns this optically distilled color, but in terms of my emotional response, I'm never prepared to see this blue.. It's always a surprise.