There are approximately 326 million trillion gallons of water in the oceans. Most of the water on Earth, about 97%, is in the oceans. The remaining 3% is in the air or in the very upper reaches of Earth’s crust. Water covers about 71% of Earth's surface, and the average ocean depth is 2.3 miles. That's a lot of water, but most of it is on the surface of the Earth.
Most of our planet is actually quite parched. Earth’s diameter is about 8,000 miles, and there is very little water in the interior. The center of the Earth is thought to be made of solid or liquid 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 dry. However, it is that 0.023% of Earth’s mass that is water which makes life, as we know it, possible.