The Earth’s total amount of water is thought to be around 344 million cubic miles. One would think that’s quite enough water to sustain us. But here are some complicating facts, courtesy of the U.S. Fish and Wildlife Service: 315 million cubic miles, or about 93 percent, of that water is seawater, meaning it’s too salty for our consumption. 2.5 percent (9 million cubic miles) is locked below the surface of the Earth, and 2 percent (7 million cubic miles) is frozen in the ice caps. Also, 53,000 cubic miles is in our lakes and rivers, 4,000 cubic miles sits in the atmosphere, and 3,400 cubic miles is in all the bodies of living things. This means that if all the water of the world could fit into a gallon jug, we would be able to use about a tablespoon.