The ocean floor is just like the dry land only covered with water. There are valleys, mountains, plains and deep trenches.
The deepest point known in the ocean is called the Challenger Deep and is located in the Marianas Trench in the South Pacifistic Ocean near Guam. (Which is over by China, Australia and Japan. It's a small island.)
The Challenger is 10,911 meters below the surface of the ocean floor. -Not the top of the water. (That's about 35,797.244 feet and that would equal almost 7 miles.)
If you put mount Everest in the Challengver, Everest would be covered by 2 kiolmeters of water. (That's over a mile of water.)
Well, that's about 11 kelometers of water all pressing down at about 1145 tons per square foot.
The first exploration of the Challenger was in January of 1960 by the crew of a sub called the Trieste. They went way down, down to the bottom of the ocean floor. It was pitch black and cold. But in the head lights of the Trieste they saw something go past. Looking closer it turned out to be a flat fish about a foot long. It just proves that GOD made every bit of the earth to be inhabited by living creatures, not excluding the deepest, coldest point in the ocean.