Ocean

An ocean is a vast body of salt water that covers much of Earth's surface and surrounds or separates continents. Earth has one interconnected global ocean, commonly divided into five named oceans: the Pacific, Atlantic, Indian, Southern and Arctic. Oceans cover about 71% of the planet's surface and contain most of Earth's water. Their depth, temperature and salt content vary from one region to another.

Ocean water is constantly moving through waves, tides and currents. Waves are mainly generated by wind, tides are driven primarily by the gravitational effects of the Moon and Sun, and currents are influenced by winds, differences in temperature and salinity, and Earth's rotation. The ocean floor is not flat: it includes continental shelves, deep basins, underwater mountain ranges, trenches and volcanic features.

Oceans are essential to life and to the functioning of Earth's climate system. They provide habitats for an enormous variety of organisms, from microscopic plankton to large marine animals, and support complex food webs. Tiny marine organisms also contribute significantly to the production of oxygen through photosynthesis. The ocean absorbs and stores large amounts of heat and carbon dioxide, helping regulate global temperatures and influencing weather and climate.

Human societies depend on the ocean for food, transport, resources and economic activities. However, marine environments face growing pressures from pollution, overfishing, habitat destruction and climate change. Rising ocean temperatures, acidification and sea-level rise are affecting many marine ecosystems. Protecting oceans requires reducing pollution, using marine resources responsibly and preserving important habitats.