Question

why water is transparent​

Answer 1

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 The range of the EM spectrum we detect corresponds to the spectrum for which water is transparent (absorbs the least). Had we evolved in mercury, we would think mercury is transparent and detect EM waves that pass through mercury.

As for the evolution of eyes, the Sun's spectrum is something like 5% ultraviolet, 45% visible and 50% infrared or lower (radio, microwaves).
Seeing ultraviolet is not such a good idea (although some animals do see it such as some insects) because it can easily damage the receptor molecules.

Hope it helps you
#be brainly