About 71 percent of the Earth's surface is water-covered, and the oceans hold about 96.5 percent of all Earth's water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers, and even in you and your dog.
Water is essential for life, and while water has been found elsewhere in the Universe, it has never been found in a form that could support life. Either too hot (vapor, steam) or too cold (ice).
As we proceed with this exploration of our environment, I will attempt to show how the oceans are utterly vital for our past and current existence. They are filled with surprises and are truly the immediate frontier for our understanding of life in the Universe!