They say you can't judge a book by it's cover. Appearances can be misleading. Turns out, that's absolutely true about the Earth. We know the surface of the Earth fairly well. We roam all of the continents. We have explored the poles, the highest mountains and the lowest valleys of the oceans. We know that water covers about 71% of the surface of the Earth.
Scientists have recently found evidence of an ocean about 400 miles below the surface of the Earth. But this ocean is estimated to be 3 times the volume of all of the water on the surface. That means there is far more water on the planet than we can imagine and it's probably been there for a very, very long time.
96% of the water on the surface of the planet is in the oceans. It is entirely possible that the water below the ground is fresh water. It is a wonder then about what kind of life might be present there. At 400 miles below, the temperatures there would almost surely support life below. I'm not sure about the pressures, but since we know that life persists at the bottom of our oceans, it's likely to have evolved there, far below the surface of the earth.
Reading about this discovery reminds me of another article I read several years ago. It was about hydrogen eating bacteria. I can't find the reference as of this writing, but what I recall is this: upon the discovery of this bacteria, they estimated the mass of such bacteria to be greater than that of all other life on the planet. Just one family of bacteria, deep below the surface, eating hydrogen at the boundary between the rocks and the water, could outweigh us all.
Perhaps we're not the rulers of the planet we make ourselves to be. But at least we won't be running out of water anytime soon.