Why is the sea blue?

Why is the sea blue?

The reason why the sea is blue has largely to with the theory of having a blue sky.

1) Sea reflects the colour from the sky

The water in the sea reflects and scatter the blue light from the sky that strikes on it, just like a mirror.

2) Sea refracts or scatters the light similar to the sky.

Since blue light has a shorter wavelength, it is refracted or scattered more than red light by the surface of water (or rather sea). Hence, we perceive sea as blue. Even if you are underwater, more blue light are scattered by the water molecules than red light and therefore the water appears blue.