What is the deepest part of the ocean?

Challenger Deep, at the southern end of the Mariana Trench in the western Pacific, is the deepest known point of the ocean, measured at roughly 35,800 to 36,000 feet depending on the survey. Mount Everest, at 29,032 feet, would sit entirely submerged with more than a mile of water above its summit. The trench exists because of subduction, where the Pacific Plate is being forced beneath the smaller Mariana Plate, creating the deep trough that characterizes plate boundaries of that type. Pressure at the bottom exceeds 16,000 pounds per square inch, over a thousand times what you experience at sea level.

Human visits remain rare. Jacques Piccard and Don Walsh reached the bottom in the bathyscaphe Trieste in 1960, and no one returned until James Cameron's solo dive in 2012, with a handful of crewed descents since. Far more people have walked on the moon. Life is nonetheless present and abundant at those depths, including amphipods, sea cucumbers, single-celled xenophyophores, and microbial communities, all sustained without sunlight. The trench has also been found to contain plastic debris and elevated levels of persistent industrial pollutants in its organisms, which is among the clearer illustrations that no part of the planet is beyond human reach even where almost no human has been.