Arm of the North Atlantic Ocean that separates Ireland from Great Britain. Connected with the Atlantic by North Channel and by St. George's Channel, it is about 130 mi (210 km) long and 150 mi (240 km) wide. Its total area is about 40,000 sq mi (100,000 sq km). Its greatest depth measures about 576 ft (175 m). The Isle of Man and Anglesey are its two principal islands.