The area of the World Ocean is 361 million km2 (139 million mi2). Its volume is approximately 1.3 billion cubic kilometres (310 million cu mi). This can be thought of as a cube of water with an edge length of 1,111 kilometers (690 mi). Its average depth is 3,790 meters (12,430 ft), and its maximum depth is 10,923 meters (6.787 mi). Nearly half of the world’s marine waters are over 3,000 meters (9,800 ft) deep. The vast expanses of deep ocean (anything below 200 meters (660 ft) cover about 66% of the Earth’s surface. This does not include seas not connected to the World Ocean, such as the Caspian Sea.

The total mass of the hydrosphere is about 1,400,000,000,000,000,000 metric tons (1.5×1018 short tons) or 1.4×1021 kg, which is about 0.023 percent of the Earth’s total mass. Less than 3 percent is freshwater; the rest is saltwater, mostly in the ocean.