Lake Superior is a lake - but I would hardly call it "just a lake" :-)

Lake Superior is the largest of the Great Lakes of North America. The lake is shared by the Canadian province of Ontario to the north, the US state of Minnesota to the west, and Wisconsin and the Upper Peninsula of Michigan to the south. It is generally considered the largest freshwater lake in the world by surface area. It is the world's third-largest freshwater lake by volume and the largest by volume in North America.[6] The furthest north and west of the Great Lakes chain, Superior has the highest elevation and drains into the St. Mary's River.
https://en.wikipedia.org/wiki/Lake_Superior

Max. length
350 mi (560 km)[2]

Max. width
160 mi (260 km)[2]

Surface area
31,700 sq mi (82,100 km2)[1]

Average depth
483 ft (147 m)[1]

Max. depth
1,333 ft (406 m)[1][3]

Water volume
2,900 cu mi (12,000 km3)[1]