The Great Lakes are a system of five large freshwater lakes in central North America—Lake Erie, Lake Huron, Lake Michigan, Lake Ontario, and Lake Superior—that drain into the Atlantic Ocean via the St. Lawrence Seaway. Combined, the Great Lakes constitute the largest surface area of unfrozen fresh water in the world: 94,850 mi² (245,660 km²), an area larger than the United Kingdom. Except for Lake Michigan, which is wholly contained in the United States, the Great Lakes form a natural segment of the U.S.-Canadian border.

Lake Superior is the largest of the five lakes by almost 10,000 mi² (41,682 km²), and has the greatest average (and maximum) depth. As a result, Lake Superior contains slightly more water than all the other Great Lakes combined—almost 3,000 mi³ (12,504 km³). The deepest parts of all the Great Lakes except Lake Erie are below sea level; in Lake Superior's case...