List of seas

Types and defining characteristics

Seas are commonly grouped by their relationship to continents and oceans. Marginal seas lie on a continental margin and are partly enclosed by peninsulas or archipelagos (for example, the North Sea). Inland or enclosed seas are largely cut off from the global ocean by landforms and often have distinctive salinity and ecology (the Caspian Sea is the largest by surface area among bodies called "sea"). Epicontinental or epeiric seas are shallow waters that once flooded continental interiors during past geological periods. Other descriptive categories include semi-enclosed seas, shelf seas and seas defined by currents rather than coasts (the Sargasso Sea).

Major seas by ocean

• Atlantic Ocean: Mediterranean Sea, Caribbean Sea, North Sea, Baltic Sea, Labrador Sea, Celtic Sea, Gulf of Guinea (often listed with seas and gulfs).
• Pacific Ocean: South China Sea, East China Sea, Sea of Japan, Bering Sea, Coral Sea, Tasman Sea, Philippine Sea, Sea of Okhotsk.
• Indian Ocean: Arabian Sea, Bay of Bengal (often treated as a large bay or sea), Andaman Sea, Laccadive (Lakshadweep) Sea, Timor Sea.
• Arctic Ocean and Southern Ocean (Antarctic): Barents Sea, Kara Sea, Greenland Sea, Chukchi Sea, Weddell Sea, Ross Sea, Amundsen Sea.

Uses, importance and threats

Seas support shipping routes, fisheries, coastal economies and a large share of marine biodiversity. They influence regional climate through heat and moisture exchange and are sites for natural resource extraction (oil, gas, minerals) and tourism. Many seas face environmental pressures: overfishing, pollution, eutrophication, invasive species and habitat loss. Sea level rise, warming and ocean acidification affect coastal communities and ecosystems, while some enclosed seas show extreme changes in salinity, water level or oxygenation due to human activities.

Distinctions, naming and notable examples

Everyday usage of "sea", "ocean", "gulf" and "bay" overlaps; technical lists vary by language, history and cartographic convention. Oceans are the largest continuous bodies of saltwater; seas are smaller and often partially enclosed. Some named "seas" are inland freshwater or brackish lakes hydrologically (Caspian Sea, Sea of Galilee) or are exceptionally saline (Dead Sea). The Black Sea has a deep anoxic layer, the Baltic Sea is markedly brackish, and the Red Sea is noted for high salinity and diverse coral reefs. International catalogues such as older editions of the International Hydrographic Organization provide one set of limits and names, but no single global list is universally accepted.

Understanding the world's seas requires attention to geography, geology, oceanography and human context: the same term can apply to shallow, productive coastal shelves, large semi-enclosed basins, or even distinctive current-defined regions of the open ocean.