why is the sea Blue? and what chemicals make the water blue.?

The sea is not blue its a reflection of the sky

The sea is blue, because the water absorbs the red and yellow parts of the visible light spectrum, and lets the blue pass through.

This can be easily demonstrated, by placing a piece of red sheet a few feet underwater (say at the bottom of a swimming pool). The sheet will appear black, because the red wavelength of light is absorbed by the water.

At depth however, even the blue wavelength will be absorbed, and below a depth of about 200 metres, there is no light at all, and the water is pitch dark.

It is true that the sea does reflect the sky colour to a certain extent; and the sea will appear grey on a dull day; but this is a surface feature only; and does not explain the overall bluish colour of the sea (or of a swimming pool, if you look through the water along the length of the pool).

SO the blue colour od sea water is due to a physical effect, known as absorption (of the red and yellow light), and not to any chemical in the water (although the dissolved salt in sea water may increase the absorption effect).

The blue colour seems evenly spread; because of a separate effect called scattering; in which the blue light gets absorbed and re-emitted by the water molecules, so that the blue light seems to be coming from everywhere (by the way; this effect; called Rayleigh scattering is why the SKY seems blue). The red and yellow light by contrast, gets absorbed by the molecules; but does not get re-emitted.

If we are talking about water other than sea water; thepresencee of fine particles in the water (for example; finely divided clay particles) may intensify the blue colour through an effect called Tyndall scattering. This is why flooded quarries sometimes appear intensely blue.

Finally, there may be materials in the sea that give the water a greenish colour. These are microscopic plants called phytoplankton; which contain greenchlorophylll (just like land based plants). If the phytoplankton are present in large quantities, then the sea can look greenish. Generally, phytoplankton are morewidespreadd in colder waters (because colder water contains more oxygen); so the polar seas can be very greenish; and the warmer tropical waters (being warmer) contain less phytoplankton, and can appear crystal-blue.

Ok you know how lakes are (usually) not clear or blue right? Well thats because of phytoplankton and theres so much that phytoplankton that is gives the river a tint, like the chlorophyll in plants. Now the ocean still has these phytoplankton, in even bigger numbers. But you know how big the ocean is, all the plankton in the world wont affect the color. And Im not sure if the salt helps at all, but it might. So thats why ocean/sea water is blue. Now drinking water is clear because well, its purified. No chemicals, no creatures, no particles of anything until your lips touch it (unless its from the faucet, in which case it contains various non harmful doses of metals and other things like arsenic and iron) So without all these other factors, the water is distilled in its most pure form and becomes clear.

The colour of the sea is determined by which wavelengths of light it absorbs and which it reflects, which in turn depends on the particles suspended in the water (mud, sand, plankton etc.). A sea in a coastal or upwelling region will have a high amount of suspended phytoplankton, which will give the sea a green hue, for example. A deep blue sea is usually associated with relatively clear water and low level of suspended particles. As some other posters mentioned, the colour and brightness of the sky will also determine the wavelengths of light that the sea will subsequently absorb/reflect.

I seen this question on the T.V. show QI.. they said it was a myth the sea is blue because it's reflected from the sky. Otherwise there would be cloud patches... the sea would be grey on a cloudy day etc. It is blue because water molecules are ever so slightly blue itself. You only notice it when there is a large mass of water. Honest. I kid you not :-)

The water isn't blue, water is colorless. The blue is coming from the reflection of the sky just as the sea would be grey on a cloudy day.

The sea is not blue, It's a reflection of blue light on the surface of the water. Google "Why is the ocean blue"

The sky isn't blue either

No chemicals, just light. The sea isn't blue it just mirrors the sky.

the sea isn't blue,it's brown.take a look at the bristol channel :)

the sea reflects the color of the sky... but if the water quality is bad, they may look green, or dull