Original: The solid surface location on the planet closest to the center of the orb is the Challenger Deep, located in the Mariana Trench at a depth of 10,924 m (35,838 ft) under the sea.
Simplified: The deepest part of all the world's oceans is a place called the Challenger Deep, which is in the Mariana Trench. It is 10,924 m (35,838 ft) under the sea.