Sunset is an optical trick, and a welcome one. The water has not changed. Near the horizon, the sun and the viewer fall into a shallow-angle arrangement, allowing reflected rays to travel directly toward the eye. Color belongs less to water than to geometry, even when the scene feels like chemistry.
The popular explanation is too tidy if it says only that the sun is low. What matters is specular reflection: countless tilted wave facets act as momentary mirrors, each obeying the law of reflection. When solar direction and viewing direction align, those facets send light toward the observer, forming the bright track called sun glitter. Cloud cover, wave slope, and position decide its width. They lose the argument.
Gold is not a dye. Long atmospheric paths remove more blue light through Rayleigh scattering, leaving the direct solar beam warmer; at grazing incidence, Fresnel reflectance also rises, making the surface more mirrorlike. A slight turn of the head can break the spell. Beyond that ribbon, the same water waits, dark and unpersuaded.
