The Mariana Trench!

The Mariana Trench is the deepest part of the world's oceans, and the lowest elevation of the surface of the Earth's crust. It is currently estimated to be up to 10,971 m (35,994 ft) deep. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about 2,550 kilometres (1,580 mi) long but has a mean width of only 69 kilometres (43 mi). It reaches a maximum-known depth of about 10.91 kilometres (6.78 mi) at the Challenger Deep, a small slot-shaped valley in its floor, at its southern end;^[1] although, some unrepeated measurements place the deepest portion at 11.03 kilometres (6.85 mi).^[2] If Mount Everest, the highest mountain on Earth at 8,848 metres (29,029 ft), were set in the deepest part of the Mariana Trench, there would be 2,076 metres (6,811 ft) of water left above it.