Deepest Sea in the World: The Mediterranean's Calypso Deep

The Mediterranean Sea is widely recognized as the deepest sea on Earth, with its maximum depth at the Calypso Deep (also called Oinousses Deep) in the Hellenic Trench, south of Greece and west of Crete.

Depth Profile

• Maximum Depth: 5,267 meters (17,280 feet) at Calypso Deep (36°34′N, 21°08′E).
• Average Depth: ~1,500 m (4,900 ft).
• Volume: ~3.75 million km³.

Why It's the Deepest "Sea"

Oceanographers distinguish seas (marginal or enclosed basins connected to oceans) from oceans (the five principal basins: Pacific, Atlantic, Indian, Southern, Arctic). While oceanic trenches (e.g., Mariana Trench at 11,034 m) are deeper, they are part of oceans, not seas.

The Mediterranean is a concentrated basin formed by the complex collision of the African and Eurasian plates, creating deep subduction trenches (Hellenic, Calabrian) within a relatively small, nearly enclosed body of water.

Other Deep Seas (for Comparison)

• Philippine Sea (marginal sea of Pacific): ~10,540 m (Philippine Trench) – but often classified as part of the Pacific Ocean system.
• Coral Sea (marginal sea of Pacific): ~9,140 m.
• Arabian Sea (Indian Ocean): ~4,652 m.
• South China Sea (Pacific): ~5,016 m.

By the strict hydrographic definition of "sea" as a subdivision of an ocean, the Mediterranean holds the record for maximum depth.