Light Spectrum
When light comes to the Earth from the Sun, the human eye can only see a narrow spectrsm of that light. This is called the visible spectrum. The human eye is sensitive to certain colors. When the Sun shines on the ocean. all colors of light enter the water. The yellow and red light is absorbed in the upper portion of the ocean. However, only the green and blue spectrum of light gets reflected back to the human eye, this is why the ocean seems blue. In other words, the color of water as seen by the human eye is a result of how light water interacts with water.