The Black Sea is a body of water and marginal sea of the Atlantic Ocean between Eastern Europe, the Caucasus, and Western Asia. It is supplied by a number of major rivers, such as the Danube, Dnieper, Southern Bug, Dniester, Don, and the Rioni. The watersheds of many countries drain into the Black Sea beyond the six that immediately border it.

The Black Sea is bordered by Ukraine, Romania, Bulgaria, Turkey, Georgia, and Russia. It has a positive water balance with an annual net outflow of 300 km3 (72 cu mi) per year through the Bosporus and the Dardanelles into the Aegean Sea.

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