When water is in a glass bottle, which is exposed to the sun, the water molecules also heat up by the bottle's walls.
But in waterfall, when water is in free fall, how does it get heated up? Does it absorb sunlight?
As far as I know, sunlight is composed of photons, right? Does it mean, that the outermost water molecules absorb all the photons, whereas the molecules "behind" get less energy from the sun (as such they heat up less)?