Color of Ocean Water

My wife and I are on vacation at Tybee Island, GA. She had a question for me that I don’t know the answer too, so I’m comming to the dope for my answers. Please don’t let me down in her thinking I know the answer to everything :slight_smile:

She wants to know, Why is the color of the water in the ocean here brownish, while when we when to the Caribbean the color of the ocean was bright blue? What causes the ocean to be a certain color somewhere, but another color elsewhere?


Silt muddying the water.

If she were to scoop some of that “bright blue” Caribbean water into a clear bottle, she would find it isn’t that color at all. The blue is a reflection of the sky.

A classic faux ami, Walloon.

Water is, in fact, blue. Not very blue, but blue nonetheless.

Water is a false cognate? Explain.

Meanwhile, NASA Oceanography: The Color of the Ocean.

Nuh-uh. Even the depth of water in my (white) bathtub is blue. Light blue, but it’s blue.

I remember being puzzled in Traditional Chinese Medicine 101 when we were learning the Chinese correspondences, and Water isn’t blue, but black! Black?! Really?! Made no sense to me…until I went to Bali. And before sunrise, when actual fisherman are going out there, the water is black. It’s really weird - the sky will lighten quite a bit and the water stayed black almost right up until the sun’s disk was visible.

I was told at the time that it was because the water was so clean - we were really seeing down to the bottom, black volcanic sand. Only once the sunlight hit it at the right angle did we no longer see the bottom, which was quite deep, but the actual blue of the water. Of course, I was told this by an old guy with no teeth native to an island of people terrified of the water, so take it with a grain or two of seasalt.

And here I believed it to be colorless, odorless and tasteless. :slight_smile:

Wiki article notes that water does indeed have a very faint blue color, based on “its frequency spectra”. I hadn’t thought of it that way before, but it makes sense. After all, astronomers use light absorption lines in the spectrum to determine what elements are in stars.

I meant “thinking water’s blueness is purely down to reflection of the sky is a common misconception (“false friend”)”. Here’s some proper academical types explaining it.

It isn’t only silt that colors sea and ocean water. There’s also algae, plankton, organics (some decomposing), and various detritus and contaminants. Not all the organics are human-related.

A half a billion years of fish pooping in it.

That beautiful clear water down in the Caribbean and other places is clear because they are basically the ocean equivalent of a desert. The brownish/greenish color is due to all the life like algae, plankton, etc. that the clear waters lack.