The World Ocean
There is really only one ocean and it is just a convention to have broken up this huge body of water into parts with different names. The ocean is the most decisive factor that makes the Earth unique among the planets. Now I have said this last night about plate tectonics so now we have two things that make the Earth unique. 70% of the Earth is covered by water and water dates back to 4.3 billion years ago. Other planets may have had water at some point in time but we are lucky to still have water because if we did not have water then we may not have the abundance of life that we see all around us.
Water has the unique property that to change one unit mass of water 1 degree C takes the highest amount of energy of any material in the world. This means that water can absorb and lose large amounts of energy with minimal changes in temperature.
It is amazing how much of living organisms is composed of water. We will touch on this again later.