There are several reasons why the ocean has been barely explored the greatest among them are that the ocean is so huge and so deep. Between the Philippines and Japan is an area of the ocean called the Mariana Trench and it is by far the deepest section of the ocean in the world. It is 1,580 miles long and 43 miles wide. As I mentioned our submarine could go 1,000 feet but the Trench is estimated to be around 36,000 feet deep!
The ocean might truly be the last frontier.