When sunlight strikes the molecules of oxygen and other compounds floating around the atmosphere of Earth, the light scatters. This scattering was first measured by English Lord Rayleigh (1842-1919) and has become known as Rayleigh Scattering. The longer wavelengths of light tend to be absorbed or reflected, and the shorter predominant wavelengths that visits our eyes tend to descend to Earth over a wide angle and are bluish in color. However, that color is not uniform; it actually appears more blue the further away from the Sun you look, where the scattering is at a maximum.
I think it's because when the sun hits the water it reflects the color. So the sky looks blue. I am not sure so do not take this for a right answer.