The Great Lakes are the largest system of fresh surface water on earth, containing roughly 18 percent of the world supply. The lakes contain enough water to cover the entire surface of the continental United States to a depth of 9 feet. The Great Lakes span more than 750 miles from west to east and their shoreline is equal to almost 44 percent of the circumference of the earth. Michigan's Great Lakes coastline alone is over 3,200 miles long, which is more coastline than any state but Alaska.
To highlight some of the interesting coastal and subsurface features of the Great Lakes, the NOAA Great Lakes Environmental Research Laboratory has assembled a narrated Google Earth tour, which you can download here. You can also watch the tour, using the Earth API, below:
The original Great Lakes bathymetric data were compiled by a NOAA (NESDIS-NGDC and OAR-GLERL) and Canadian Hydrographic Service team from archival U.S. and Canadian soundings spanning more than 75 years. Dr. David Schwab (GLERL) generated a gridded 3-arc second dataset from the NOAA-CHS project and provided it to Google to form the basis for the Great Lakes topography.