Measuring the Greatest Ocean Depth The Challenger Deep in the Mariana Trench is the deepest known point in Earth's oceans. In 2010 the United States Center for Coastal & Ocean Mapping measured the depth of the Challenger Deep at 10,994 meters (36,070 feet) below sea level with an estimated vertical accuracy of ± 40 meters. If Mount Everest, the highest mountain on Earth, were placed at this location it would be covered by over one mile of water.