Which two bodies of water are connected by the Bosporus?

The Bosporus, also known as the Strait of Istanbul, is a narrow, natural strait and an internationally significant waterway located in northwestern Turkey. The Bosporus connects the Black Sea with the Sea of Marmara. It is the world's narrowest strait used for international navigation.

It is 30 kilometres (19 miles) long with the maximum width of 3.7 kilometres (2.3 miles) at the northern entrance and minimum width 750 metres (2,450 feet) between two Ottoman-era forts, Rumeli and Anadoluhisari. The depth ranges from 36.5 metres to 124 metres (120 to 408 feet) midstream.

As part of the only passage between the Black Sea and the Mediterranean, the Bosporus has always been of great importance from a commercial and military point of view, and is strategically important today. It is a major sea access route for numerous countries, including Russia and Ukraine. Control over it has been an objective of a number of conflicts in modern history: the Russo-Turkish War (1877–78), as well as of the attack of the Allied Powers on the Dardanelles during the 1915 Battle of Gallipoli in World War I.

Navigation is extremely difficult in the Bosporus. There are sharp turns and strong and complex currents. Changeable weather conditions also hamper navigation. A ship in the Strait can be swiftly surrounded by heavy fog reducing visibility to zero. Boats must use an experienced pilot to guide them through.The throughput capacity of the Bosphorus, is estimated at 200 million tons.