What Is the Sea?

Seas are large bodies of water located between landmasses and filled with saltwater. Approximately 71 percent of the Earth’s surface is covered by water, most of which consists of seas. Seas, which are smaller than oceans, are sometimes connected to oceans (such as the Mediterranean Sea) and sometimes exist as inland seas (such as the Caspian Sea).

Millions of years ago, lava emerging from within the Earth cooled to form the crust. Over time, the dense water vapor in the atmosphere condensed into rain, and these waters accumulated in the low-lying areas of the Earth’s surface to form seas.

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- Salty: Seawater contains an average of 3.5 percent salt.

- Rich in life: Home to millions of organisms such as fish, corals, seaweeds, and microscopic plankton.

- Dynamic: Seas are in constant motion due to waves, tides, and currents.

- Variable depth: Some seas are only a few meters deep while others reach thousands of meters in depth.

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- A source of fish and marine products.

- Serve as major routes for trade and transportation.

- Help regulate the climate.

- Contain natural resources such as salt, oil, and natural gas.

- Used for recreation and tourism.

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Türkiye is a peninsula surrounded by seas on three sides:

- The Black Sea

- The Sea of Marmara

- The Aegean Sea

- The Mediterranean Sea

These seas directly influence both nature and human life.

National Geographic Kids. “What Is the Ocean?” Accessed 9 July 2025. https://kids.nationalgeographic.com/nature/oceans/article/ocean

TÜBİTAK Bilim Genç. “How Were Seas Formed?” Accessed 9 July 2025. https://bilimgenc.tubitak.gov.tr/makale/denizler-nasil-olustu

NOAA. “What Is the Difference Between an Ocean and a Sea?” Accessed 9 July 2025. https://oceanservice.noaa.gov/facts/oceanorsea.html