channel, about 60 miles (100 km) long and nearly 30 miles (50 km) wide, between Yorke Peninsula to the north and Kangaroo Island to the south, leading eastward from the Indian Ocean into Gulf St. Vincent, South Australia. It merges (east) with the Backstairs Passage (channel), and its western entrance is marked by the three rocky Althorpe Islands, which rise to 285 feet (87 metres). The strait is used as an approach to Adelaide on the gulf coast and as an area for game fishing. It was navigated in 1802 by the English explorer Matthew Flinders and is named after his ship.