Why is the sea blue, because the water itself is transparent? And even if you take sea water and pour into the decanter, it will also be transparent.
Wrong answer: because the sea reflects the sky and it is blue.
The color of the sea, which we see is the result of scattering of sunlight thickness of sea water.
Water passes light unevenly - short wave it dissipates better and long - worse. Short waves correspond to the blue part of the spectrum, and a long red. In the Countess you look at the clearance on the thin layer of water, therefore the difference in the transmission of invisible rays. And in the sea you can see the result of the scattering of sunlight multimeter water. So the blue light is less absorbed in water, and in the light that emerges FROM the water, mostly blue color.
By the way
Best water reflects blue and purple color. And even better - ultraviolet rays. That is why the sea is a danger of getting sunburn higher than away from water.