Why the Ocean is Blue

Most recent answer: 04/22/2013

Why is ocean blue in color?
- Naman Kumar Karn (age 14)

It is a common misconception that the ocean looks blue simply because it reflects the blue sky. However, that is not true. The ocean looks blue because water absorbs long wavelength visible light (red, orange, yellow) more than small wavelength visible light (blue). When white light (which consists of all colors of visible light) comes from the sun and goes into the ocean, the different colors are able to penetrate to different depths before being completely absorbed. As you can see from the image below, blue has the largest penetration depth which means blue is the least absorbed color in the visible light spectrum so most of the light that escapes the water and reaches our eye is blue. For this reason, the ocean looks blue. 

A glass of water appears clear because the amount of water is too small for this effect to be noticeable and all the colors are able to reach our eye. The ocean is deep enough to see that water itself is blue. If you are further interested, you can check out NASA's website on this subject:


(published on 04/22/2013)