Lake Huron is the second largest of the Great Lakes and the fifth largest in the world, with the most irregular shape of any of the Great Lakes. Even its largest island, Manitoulin, is wider than the State of Rhode Island, and has five small lakes of its own. The lake is connected with its neighbor, nearly same-sized L. Michigan, only by a narrow straight called the Straights of Mackinac, which is spanned by a 8 km-long bridge, the Mighty Mac. The shores around Mackinac offer spectacular landscape. The water quality of the lake is still excellent and oligotrophic. Transparency is generally recorded at 8 m, and chlorophyll a concentration at the lake centre is less than 2 micro l-1. However, the water in Saginaw Bay in the southern part has become considerably worse due to the nutrient loading from surrounding areas.

Many long freighters and other seafacing vessels come and go on this "inland sea". In summer, recreational boating and yacht-racing are supported by many local clubs almost every day.