Korea Strait is a sea passage between the East China Sea and the Sea of Japan (in South Korea known as the East Sea). To the north it is bounded by the south coast of the Korean peninsula, to the south by the Japanese islands of Kyushu and Honshu. The strait has a depth of about 90 metres and is split by the Tsushima islands. To the east the Korea Strait is often referred to as Tsushima Strait, to the west it was formerly known as Chosen Strait. In another classification, the whole strait is called Tsushima Strait. In this case, the West Channel is called Korea Strait.
A branch of the Kuroshio (Japan Current) passes through the strait. It is the warm branch called Tsushima Current. Originating along the Japanese islands this currents eventually flows into the Pacific and the Sea of Okhotsk near Sakhalin. The Korean Strait was the location where in 1905, during the Russo-Japanese War, the Japanese fleet annihilated theit Russian counterpart. This key battle is often referred to as the Battle of Tsushima.