The issue is even more complicated. The absorbtion at the red end of the visual spectrum is two magnitudes larger than at the blue end. This is why water appears often blue, even against a white background.
This reminds me of the time I went looking for a satisfactory answer for why the sky is blue.
It turns out a surprising number of people have a surprising number of different opinions and explanations on this. You pretty much need a PhD in physics to fully grok most of them. And every time you think you've read something that at least _sounds_ concrete, someone else comes along and says, "yes and no, the _real_ mechanism is this," ad infinitum until you wind up on the fringes of scientific knowledge.
In the end, hours of research later, as best as I could tell, it came down to: the sky is blue because air is blue. But it's a very faint blue, so you can't actually discern the blue until you look through a _lot_ of air, for example in the sky.
Things have color because they scatter/reflect/refract/absorb/emit differently for different colors of light.
Air looks blue because it scatters blue light more than other colors. The blue components of sunlight reach you from all parts of the sky, while the non-blue components reach you mostly from the direction of the sun. At sunset, sunlight from the direction of the sun passes through much more atmosphere than during the day and most of its blue light scatters away, leaving red and yellow. [0] If air didn't scatter light, the sky would be black like it is on the moon.
Air is a gas. Gasses do not reflect light.
Air refracts sunlight and makes the sun appear flattened at the horizon [1].
Air absorbs most non-visible colors (UV and IR) [2]. Animals evolved eyes to see only the colors of available light.
Because people haven't really explained the specific mechanisms:
You can think of a material as a bunch of simple harmonic oscillators, which are driven by an applied field (electric or magnetic). These oscillators have different natural frequencies, and so couple to different wavelengths. For instance, if you play a loud note next to a piano, you can see the corresponding piano string start to vibrate, but the others may not.
The interaction between these oscillators and the wave are what lead to the dielectric constant (and therefore the slowing of waves), as well as absorption (which can be thought of as the imaginary component of the dielectric constant).
In a real material, these "oscillators" are really any method of energy storage that can couple to the motion of charges (i.e. current). These include, but are not limited to:
- rotations (in a gas or liquid)
- vibrations (in any state)
- electronic transitions
- electronic movement (in the case of a metal)
- displacement (in any state)
In a single molecule, many of these mechanisms would have discrete natural frequencies. But in a solid or liquid, interactions lead to a continuous band structure (especially for things like vibrations).
For water specifically, the below visible range is quickly absorbed by vibrational and rotational energy modes, while the high end of the UV range is absorbed by electronic transitions. Other materials have similar sweet spots for transmission, but at different frequencies. For instance, materials like indium tin oxide (ITO) are designed to be conductive, but not at the high frequencies of visible light, making them transparent. As another example, metals are reflective below their plasma frequency (related to the speed the 'electron sea' can move at), and transparent above (X-rays operate in this region of transparency).
If you want more information, I can recommend "Optical Properties of Solids" by Mark Fox.
I think this reasoning may be right, if expressed backward. "Visible light" is just that which life evolved to care most about, because it was what was available in the (shallowish) water.
in the case of the whales, whom returned to the deep sea 40-50mya and have since rarely had a use for visible light, it's interesting to wonder what they have evolved to care most about if no longer visible light, especially in the sense of their song, and when you compare the visual acuity of their cousins the dolphins in the same timespan, and the incredible hyper-evolution of the human eye since ~1mya
