the following facts caught my eye:    

                         An estimated 80% of all life on earth is found under

                         the ocean surface and the oceans contain 99% of the

                         living space on the planet. Less than 10% of that

                        space has been explored by humans. 85% of the area

                        and 90% of the volume constitute the dark, cold environment

                        we call the deep sea. The average depth of the ocean is

                        3,795 m (12,450 feet). The average height of the land is

                        840 m. (2,755 feet)

                         The oceans cover 71% of the Earth's surface and

                         contain 97% of the Earth's water. Less than 1% is fresh

                         water, and 2-3% is contained in glaciers and ice caps.

     this is from a wonderful site, Marinebio.org.   it is just full of

information and useful stuff, including full details and pictures on

quite a number of species, quizzes, and news.