Why Usually Blue?
◆ Have you ever wondered why the ocean is usually blue? It is because tiny particles suspended in the water scatter the sunlight. Being of a short wavelength, blue light is scattered more effectively than light that is of longer wavelengths. This is basically the same reason why the sky is blue. Of course, in some areas microscopic floating plants add a yellow pigment, giving the water a greenish appearance. Or, suspended silt in the water can give it a brownish hue, as near the outflow of large rivers.