Why is the ocean sometimes blue and sometimes green?

Answer 1

There are several theories:
Blue wavelengths are absorbed the least by the deep ocean water and are scattered and reflected back to the observer’s eye
Particles in the water may help to reflect blue light
The ocean reflects the blue sky
Most of the time the ocean appears to be blue because this is the color our eyes see. But the ocean can be many other colors depending upon particles in the water, the depth of the water, and the amount of skylight.
The colors we see depend upon the reflection of the visible wavelengths of light to our eyes. The Franklin Institute provides a good explanation of how we see color at http://www.fi.edu/color/color.html.
Wavelengths of light pass through matter differently depending on the material’s composition. Blue wavelengths are transmitted to greater depths of the ocean, while red wavelengths are absorbed quickly. Water molecules scatter blue wavelengths by absorbing the light waves, and then rapidly reemitting the light waves in different directions. That is why there are mostly blue wavelengths that are reflected back to our eyes.
Sometimes oceans look green. This may be because there is an abundance of plant life or sediment from rivers that flow into the ocean. The blue light is absorbed more and the yellow pigments from plants mix with the blue light waves to produce the color green.
Sometimes parts of the oceans will look milky brown after a storm passes. This is because winds and currents associated with the storm churn up sand and sediment from the rivers that lead into the oceans.
The ocean may also reflect the blue sky. However this is prominent only at relatively low angles and when the water is smooth.

Answer 2

When there is a lot of water, and the water is very deep so that there are no reflections off the sea floor, the water appears as a very dark navy blue. The reason the ocean is blue is due to the absorption and scattering of light. The blue wavelengths of light are scattered, similar to the scattering of blue light in the sky but absorption is a much larger factor than scattering for the clear ocean water. In water, absorption is strong in the red and weak in the blue, thus red light is absorbed quickly in the ocean leaving blue. Almost all sunlight that enters the ocean is absorbed, except very close to the coast. The red, yellow, and green wavelengths of sunlight are absorbed by water molecules in the ocean. When sunlight hits the ocean, some of the light is reflected back directly but most of it penetrates the ocean surface and interacts with the water molecules that it encounters. The red, orange, yellow, and green wavelengths of light are absorbed so that the remaining light we see is composed of the shorter wavelength blues and violets.

The reason the ocean looks green sometimes is due to the phytoplankton content. The most important light-absorbing substance in the oceans is chlorophyll, which phytoplankton use to produce carbon by photosynthesis. Due to this green pigment - chlorophyll - phytoplankton preferentially absorb the red and blue portions of the light spectrum (for photosynthesis) and reflect green light. So, the ocean over regions with high concentrations of phytoplankton will appear as certain shades, from blue-green to green, depending upon the type and density of the phytoplankton population there.

Answer 3

Blue = light reflected
green = chlorophyll in floor of the ocean

Answer 4

when the ocean looks green theres a lot of plankton in the water

Answer 5

On calm hot n sunny days it creates the elegy in it to grow a lot more which will give the water the very green tint.

Answer 6

The water is really colorless, when it's blue it's the sky's reflection, when it's greenish there's alot of algae or plankton.

Answer 7

I think it has something to do with the reflecting the sky theory...

Answer 8

if it is green that means someone just peed there, so you better get out real quick

Answer 9

I think maybe because of algae. I don't think I spelled it right.