Why does ocean water look more blue in some places?

Question

Like in Miami, or in the Caribbean, the water is very blue. But go farther north to, for example, Jacksonville, and the water is a darker color. What's the reason for this?

Answer 1

most likely less pollution... is it brown, wear its not blue.... then its definately pollution...

Answer 2

The sea appears blue, for a similar reason why the sky seems blue: The sky is blue because the molecules in the atmosphere scatter the blue part of the spectrum, and the red and yellow parts of the spectrum tend to pass straight through.  To us looking from the ground, the blue light seems to be coming from everywhere (this is called 'Rayleigh cattereing'); hence the sky seems blue.

The reason why the sea seems blue is similar; but a little more complicated.  The sea does reflect the blue colour of the sky (or can appear grey in overcast weather), but this only applies to the surface of the sea.  As well as reflecting the blue from the sky, the water molecules scatter the blue light in much the same way as the air molecules in the sky.  This accounts for the 'natural faint blue colour'.

In addition,  the water also absorbs more of the red and yellow wavelengths (which warm the sea), leaving the blue part of the spectrum, as well as part of the green.  This is why deep water can appear bluish-green. (The absorption of the red wavelengths can be noticed by looking at a red object under deep water.  It will appear black; because only blue light is reflected back to us.)

Eventually, at sufficient depth, even the blue light will have been absorbed or scattered away, and deep water will be black and lightless.

This scattering effect is even stronger if there are colloidal materials (very finely divided particles) in the water, such as finely divided clay particles.  These can increase the scattering effect, turning the water an intense blue (which can sometimes be seen in flooded abandoned quarries).  The scattering effect is also greater with ice; which results in the intense blue colour we see if we look down a crevasse in a glacier, or down a hole in the snow made by a ski stock..

Anything in the water will change the way the light gets scattered or absorbed.  The two most common variations are pollution (not just man made; but also muddy fresh water brought down by rivers) and, as another answerer said, by phytoplankton.  The clearer the water, the more blue it will appear.  Another factor is that the tropical waters are often shallow, with a bright sandy bottom, and not deep enough to absorb the blue light.  In temperate areras, especially maritime coastal areas, the water is deeper, and the blue light is absorbed; leaving a dirty green colour.

For complete, scientific explanations of the scattering effect, look up 'blue sky' in Wikipedia.

Answer 3

amount of pollution, the way the sun hits the water, and how the sky looks. water generally reflects the same color as the sky. in the Caribbean the sky is blue with lots of light there for so is the water. also the water type is different. the farther you get from the equator the colder the water is. in the Caribbean the water is in a sea ( in a giant cove) - it is not open water. the open ocean tends to be darker. also the depth of the water.