Terrain: In the ocean, it is 71% water. It is very dark, and that is why they call it the dark zone. The Puerto Rican Trench is the deepest part out of the oceans and trenches. It was thanks to fine machinery, because now we know about the very gross creatures living in the depths of the sea,and just how deep it actually is, and the oceans that the scientists use to discover new life for us. There have only been two people to go down to the dark zone, and lived to tell the tale.