When we were small, we thought the ocean is blue because the sky is blue. But, did you ever think even the sky appears white or orange, yet still the ocean blue.
The main reason for the ocean to be blue is the way water molecules absorb and scatter the colors of sunlight. Sunlight is essentially all colors mixed together, which appear to our eyes as white. Rainbows are light from the sun and when separated in to its colors. These are red, orange, yellow, green, blue, indigo and violet. When sunlight falls on the ocean, the rainbow colors red, orange, yellow and green are absorb into the water because they have longer wavelength. This is because different waves of light make water molecules vibrate in different ways. The colors blue, indigo and violet colors are not absorb as much, and there for scattered around which makes ocean appear blue. Simply put, ocean water looks blue because that’s the only color of sunlight left after the colors were absorbed.
Why is the depth of the ocean completely dark?
The average depth of the ocean is about 12,100 feet. And when the sunlight passes deep in to the ocean almost all of the red light has been absorbed. Now the blue shades penetrate deeper into the ocean and eventually they also get absorbed. This is why oceans are completely dark below about thousand miles deep.