There are approximately 326 million trillion gallons of water in the oceans. Most of the water on Earth, about 97 percent, is in the oceans. The remaining 3 percent is in the air or in the very upper reaches of Earth’s crust. Water covers about 71 percent of Earth's surface and the average ocean depth is 2.3 miles. This makes the oceans seem immense, but most of our planet consists of minerals. Earth’s diameter is about 8,000 miles and there is very little water in the interior of the Earth.
The center of the Earth is thought to be made of solid iron surrounded by an iron-nickel alloy, which is further surrounded by layer upon layer of rocky materials of generally decreasing density, mostly with little or no water. Taken as a whole, the planet is quite parched. However, it is that 0.023 percentage of Earth’s mass that is water which makes life, as we know it, possible.