Oceans cover about 70% of the Earth's surface. The oceans contain roughly 97% of the Earth's water supply.
The oceans of Earth are unique in our Solar System. No other planet in our Solar System has liquid water (although recent finds on Mars indicate that Mars may have had some liquid water in the recent past). Life on Earth originated in the seas, and the oceans continue to be home to an incredibly diverse web of life.
The oceans of Earth serve many functions, especially affecting the weather and temperature. They moderate the Earth's temperature by absorbing incoming solar radiation (stored as heat energy). The always-moving ocean currents distribute this heat energy around the globe. This heats the land and air during winter and cools it during summer.
The Earth's oceans are all connected to one another. Until the year 2000, there were four recognized oceans: the Pacific, Atlantic, Indian, and Arctic. In the Spring of 2000, the International Hydrographic Organization delimited a new ocean, the Southern Ocean (it surrounds Antarctica and extends to 60 degrees latitude).
There are also many seas (smaller branches of an ocean); seas are often partly enclosed by land. The largest seas are the South China Sea, the Caribbean Sea, and the Mediterranean Sea.
Ocean / Area (square miles) / Average Depth (ft) / Deepest depth (ft)
Pacific Ocean / 64,186,000 / 15,215 / Mariana Trench, 36,200 ft deep
Atlantic Ocean / 33,420,000 / 12,881 / Puerto Rico Trench, 28,231 ft deep
Indian Ocean / 28,350,000 / 13,002 / Java Trench, 25,344 ft deep
Southern Ocean / 7,848,300 sq. miles (20.327 million sq km ) / 13,100 - 16,400 ft deep (4,000 to 5,000 meters) / the southern end of the South Sandwich Trench, 23,736 ft (7,235 m) deep
Arctic Ocean / 5,106,000 / 3,953 / Eurasia Basin, 17,881 ft deep