Oil has a density less than that of sea water; therefore, oil floats. In general, most of the oil spreads on the surface of the water and it will cover a large expanse and will not be very think in any one place. In time the sun's heat and radiation hardens some of the oil. Part of it evaporates (the lighter portions anyway) and some of the heavier parts tend to cling together and form "tar balls". The tar balls sink to the bottom. Wind action spreads the oil more and some of the tar balls are washed ashore. In my opinion, the most damage is caused by oil at the shoreline. It adheres to the vegetation and can't be diluted as much as it can as long as it stays far off shore. I'm sure you can go to www.google.com and find a number of sites that will give you some basic scientific information about mixing oil and water.I caution you against taking everything you read about the oil spill in the gulf as fact. Much of the information is tainted with opinion, much of which is not based on good scientific data/research.
