Welllll.. there's 200 feet between the water and roadbed..
We talked to the FBO guy in St. Ignace (town on the north end of the bridge). He said it happens more times than you'd think. If you just "do it" and don't make a spectacle of it (dive from 2000 ft and shoot skwards after passing under.. you just might get away with it.
I believe some old Air Force guy did it in a BOMBER !