It is hard to comprehend the enormity of the Great Lakes. These are not really lakes; they are more like inland seas.
Allow me to blow your mind with a statistic:
The Great Lakes contain 5,472 cubic miles of water: roughly 22% of the world’s fresh water supply. The Great Lakes have enough water to cover the entire United States, and to do so at a uniform depth of 9.5 feet(!).
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From my hotel room window in Sault Ste. Marie, I have a picturesque view of the "locks" which connect Lake Huron and Lake Superior by enclosing ships between two steel walls and allowing thousands of gallons of water to rush in or seep out, depending on whether the ship is destined for the higher waters of the Superior, or the lower waters of the Huron. The hotel lobby also has a way-cool 3D topographic map of the lakes, which, unfortunately for you, I was unable to reproduce with a google search. From looking at a 2D map of the lakes, one could easily falsely assume that these five lakes are pretty similar in size and depth, but you'd be oh so wrong. Take a look at this chart taken from Wikipedia:
