Extension of Hudson Bay, located between northern Ontario and Quebec, Can. Generally less than 200 ft (60 m) deep, it is 275 mi (443 km) long and 135 mi (217 km) wide. It contains numerous islands, of which the largest is Akimiski Island. The many rivers that empty into the bay, including the Moose, are the cause of its low salinity. Visited by Henry Hudson in 1610, it is named for Capt. Thomas James, who explored it in 1631.