Hitting Bottom: Submariner Explored Deepest Part of Ocean Thousands have climbed Mount Everest, and a handful of people have walked on the moon. But reaching the lowest part of the ocean? Only three people have ever done that, and one was a U.S. Navy submariner. In the Pacific Ocean, somewhere between Guam and the Philippines, lies the Marianas Trench, also known as the Mariana Trench. At 35,814 feet below sea level, its bottom is called the Challenger Deep — the deepest point known on Earth. In fact, to put it into perspective, think about the Titanic, which was found 12,600 feet below the surface of the Atlantic Ocean — nearly 2.4 miles down.