Question

Why does the surface of a lake appear blue in color on a clear day

Answer 1

Its because when white light from the sun goes into the ocean, the color blue mostly forms, from the short wavelength light.

Hope this helps :)

Answer 2

because it reflects the color of the sky? "The ocean looks blue because red, orange and yellow (long wavelength light) are absorbed more strongly by water than is blue (short wavelength light). So when white light from the sun enters the ocean, it is mostly the blue that gets returned.