The average ocean depth is 2.5 miles (4 km).

The average depth of the oceans is about 4 km. More precisely the average depth is 3,688 meters (12,100 ft). Nearly half of the world’s marine waters are over 3,000 meters (9,800 ft) deep. “Deep ocean,” which is anything below 200 meters (660 ft.), covers about 66% of Earth’s surface. This figure does not include seas not connected to the World Ocean, such as the Caspian Sea.

The deepest part of the ocean is called the Challenger Deep (11 km) and is located beneath the western Pacific Ocean in the southern end of the Mariana Trench, which runs several hundred kilometers southwest of the U.S. territorial island of Guam.

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