Bering Strait, a narrow, shallow channel that separates Siberia from Alaska and connects the Pacific and Arctic oceans. The strait is about 50 miles (80 km) wide at its narrowest point and has depths up to about 170 feet (52 m). It is choked with sea ice during much of the year, but is never completely frozen. The International Date Line cuts through the middle of the strait, between Little Diomede Island (United States) and Big Diomede Island (Russia). The two islands are only 2 1/2 miles (4 km) apart. The strait was discovered by Semen Dezhnev, a Russian navigator, in 1648. It was named for Vitus Bering, a Dane, who explored it in 1728.