The Pacific Ocean is the largest body of water on Earth, covering approximately 165.25 million km² — more than all of the world's landmasses combined. It also contains the deepest point on the planet: the Challenger Deep in the Mariana Trench, which plunges roughly 10,935 meters below the surface. The Pacific's average depth is about 4,280 meters (14,040 feet), reflecting the vast volumes of water filling its enormous basin, and together these figures make the Pacific the dominant feature of the global ocean system.
The Atlantic Ocean is the second-largest, extending over approximately 106.46 million km², with an average depth near 3,646 meters (11,962 feet). The Indian Ocean, the third-largest at about 70.56 million km², has a slightly deeper average floor of around 3,741 meters (12,274 feet). Together with the Pacific, these three oceans account for the overwhelming majority of Earth's saltwater, and each plays a major role in global climate, shipping, and marine biodiversity.
The Arctic Ocean is the smallest and shallowest of the world's five oceans, covering only about 14.06 million km² and averaging just 1,205 meters (3,953 feet) in depth. The Southern Ocean, which surrounds Antarctica, was not officially recognized as a distinct body of water until the International Hydrographic Organization formally identified it in the year 2000, and it spans roughly 20.33 million km². These two polar oceans are increasingly in the scientific spotlight because warming climates are changing their ice cover, salinity, and ecosystems faster than anywhere else on the planet.