The ocean's average depth is 2.65 miles, which is equivalent to roughly 14,000 feet. The deepest known area of the ocean, Challenger Deep in the Marianas Trench, is 36,200 feet deep, 6.86 miles from the surface.
The ocean is typically divided into zones based on depth. The aphotic, or lightless, zone of the ocean varies with water turbidity and season, but it generally starts 660 to 3,300 feet from the surface. The photic zone, coterminous with the pelagic zone, is the uppermost area of the ocean. Below the pelagic zone is the benthic area, which is comprised of the bathyl, abyssal and hadal zones. The benthic zone begins less than half a mile from the surface and extends to the deepest trench areas.