It is due to Rayleigh Scattering of smaller wavelengths by tiny water molecules floating just above the surface of sea.
The color of a lake may just be the color of the sky, reflected in the lake, but if the water itself is actually greenish blue, that is caused by algae.
turquoise
If you are referring to the different depths of blue and green, it is because the deeper the water is, the darker the color. The reason for this is because the deeper the water, the less sunlight can penetrate through to the floor and reflect back out.
In general open expanses of water reflect whatever colour is predominant in the environment. This usually tends to be the sky colour. If the sky is clear, water in the sea or lakes will appear blue. If the sky is dull, so also will be the water surface. The tap water in the glass will still usually be clear.
sea water doesnt freeze faster than fresh water, fresh water freezes faster than sea water as it has a lower freezing point than sea water has as sea water contains salt which makes the boiling/freezing points increase therefore making the sea water freeze at a lower temperature.
The colour of the sea is greenish blue because of the reflection of the sky
The sea water is a greenish blue colour, (The greenish colour comes from the abundant plankton that thrive within the water.)
The color of sea water varies with the location. Near the shore, the water stirred up in the surf is more greenish, but way out to sea, deep water is more dark blue.
Water appears greenish blue because its complimentary color red is absorbed by water molecules
a greenish blue color
The color of a lake may just be the color of the sky, reflected in the lake, but if the water itself is actually greenish blue, that is caused by algae.
The correct answer is clear, but maybe thats not what you are asking. I spent 8 years on sea duty in the US Navy, the color of sea water changes depending on where you are. Some places it is a beautiful light blue, and others its a dark blue almost greenish color. Usually the further you get from shore the better the water looks but thats not always the case.
It should be a greenish blue.
turquoise
It seems a joke, but it isn't: sea is blue because water surface reflects the colour of the sky (blue, indeed). Then, if you want to know why the sky is blue, look for that question (it's very hard to explain it in few words, or in a few formulae: it involves refraction and trasmission of light; optics and electrodynamics!)
The correct answer is clear, but maybe thats not what you are asking. I spent 8 years on sea duty in the US Navy, the color of sea water changes depending on where you are. Some places it is a beautiful light blue, and others its a dark blue almost greenish color. Usually the further you get from shore the better the water looks but thats not always the case.
Because it absorbs the longer reddish wavelengths. Links: http://www.whyiswaterblue.com/ http://en.wikipedia.org/wiki/Color_of_water http://www.webexhibits.org/causesofcolor/5B.html