Everyone will say that the water is clear. And actually it is transparent only in a thin layer. At the bottom of oceans night, because the sun's rays cannot pass through the whole water column.
But not only water - all substances in a thin layer of transparent and thick no. Take, for example, a piece of white, transparent glass and look at him in the ribs. The glass will seem and not white and not transparent.
One scientist was prepared from iron plate thickness of one hundred-thousandth of a millimeter. Record this as transparent as glass, and almost colorless. Putting it on the book page, you can easily read the fine print.
The same transparent plate scientist prepared of gold and other metals.