Wait...water...bridge...under water? water under...over...water bridge over water? My meager brain can't handle the concept and is about to explode.
We've done the same thing. Back when the Revolution was still within living memory, the Chesapake and Ohio Canal was built to carry water traffic from the Potomac River to (I think) the Ohio Valley. Much of it remains today- including a small stretch in Georgetown where you can still ride the towboats.
Incidentally, the Watergate Hotel of Nixonian fame, was named for the canal's 'water gate', where the canal met the Potomac River. You can still see the original water gate today.
http://mcmullans.org/canal/aqueduct.htm