The ocean covers 70 percent of Earth's surface.
It contains about 1.35 billion cubic kilometers (324 million cubic miles) of water,
which is about 97 percent of all the water on Earth. The ocean makes all life on Earth possible,
and makes the planet appear blue when viewed from space. Earth is the only planet in our solar system that is definitely known to contain liquid water.
The average depth of the oceans is about 4 km.
More precisely the average depth is 3,688 meters (12,100 ft).
Nearly half of the world's marine waters are over 3,000 meters (9,800 ft) deep.
"Deep ocean," which is anything below 200 meters (660 ft.), covers about 66% of Earth's surface.
This figure does not include seas not connected to the World Ocean, such as the Caspian Sea.
The deepest region of the ocean is at the Mariana Trench, located in the Pacific Ocean near the Northern Mariana Islands.
The maximum depth has been estimated to be 10,971 meters (35,994 ft).
The British naval vessel Challenger II surveyed the trench in 1951 and named the deepest part of the trench
the "Challenger Deep". In 1960, the Trieste successfully reached the bottom of the trench, manned by a crew of two men.