Why is the sea blue?

Why is the sea blue some places and green other places?

Color's a tricky thing to understand. Every single color you see is an ingredient in pure white light. (Sunlight is a good example of white light.) A rainbow lets you see the main ingredients in white light -- red, orange, yellow, green, blue, indigo and violet. Colors such as light blue, pale green or fuchsia are there, too.

What colors you see depends on which colors of white light are absorbed by an object, and which colors bounce back to your eyes. Say you are looking at a red book. The chemical and physical make-up of the book lets it absorb all the colors except red. The red bounces off the book and back to your eye.

And the sea? Well, scientists don't agree on this one. Some say light from the blue sky reflects off the water to you eye, and that color of water itself is greenish-blue. Others say water is blue, and that oceans look green along the coasts because underwater plants reflect more green.

Either way, the next time you go for a dip in the sea, look closely. There's more to water's color than meets the eye!

Why Is The Sea Blue

The short answer is that it's reflecting the color of the sky.

Sorry, I didn't read your entire question so you already knew about the reflection of the sky. I would guess (emphasis on the word guess) that the photos you see of our "blue planet" are taken with enough sunlight hitting the earth for the effect to continue. The water certainly looks much darker blue when seen from afar.

I think it's because when the sun strikes one of the particles in the sea, it reflects to another particle, and so on. It doesn't always have to be blue.

Rayleigh scattering (named after Lord Rayleigh) is the scattering of light by particles much smaller than the wavelength of the light. It occurs when light travels in transparent solids and liquids, but is most prominently seen in gases. Rayleigh scattering of sunlight from particles in the atmosphere is one reason light from the sky is blue.