An estimated 6000 ship wrecks....so far.
The Great Lakes, a collection of five freshwater lakes located in North America, have been sailed upon since at least the 17th century, and thousands of ships have been sunk while traversing them. Many of these ships were never found, so the exact number of shipwrecks in the Lakes is unknown; the Great Lakes Shipwreck Museum approximates 6,000 ships and 30,000 lives lost,[1] while historian and mariner Mark Thompson has estimated that the total number of wrecks is likely more than 25,000.[2] In the period between 1816, when the Invincible was lost, to the sinking of the Fitzgerald in 1975, the Whitefish Point area alone has claimed at least 240 ships.
http://en.wikipedia.org/wiki/List_of_shipwrecks_in_the_Great_Lakes
