The deepest part of the ocean that humans have explored is the Challenger Deep, located in the Mariana Trench in the western Pacific Ocean. The Mariana Trench is the deepest known oceanic trench on Earth, and the Challenger Deep is its deepest point.
The depth of the Challenger Deep was first measured and explored by the British survey ship HMS Challenger in 1875, which is where its name comes from. Since then, several expeditions and manned submersible dives have further explored and studied the depths of the Challenger Deep.
The depth of the Challenger Deep is approximately 10,928 meters (35,856 feet) below sea level. To put this into perspective, it is nearly 7 miles deep, making it the deepest known part of the world’s oceans.
In 1960, Swiss engineer and oceanographer Jacques Piccard and U.S. Navy Lieutenant Don Walsh made history by descending to the Challenger Deep in the submersible Trieste. They remain the only humans to have reached the Challenger Deep until recently. In 2012, filmmaker James Cameron made a solo dive to the Challenger Deep in a specially designed submersible.
The exploration of the deep ocean continues to be an area of scientific interest, and unmanned deep-sea vehicles and remotely operated submersibles have been used to explore and study the extreme depths of the Challenger Deep and other parts of the ocean floor.