Challenger Deep, the deepest known point on the Earth, is located in Pacific Ocean's Mariana Trench 36,070 feet below sea level while Earth's tallest peak Mount Everest has an altitude of 29,029 feet above sea level. Interestingly, about 90% of all marine life live within 660 feet of the ocean surface. Mariana Trench was discovered on March 23, 1875.