AKA the SAUTE-MOUTONS. Those French Canadians are out of their minds with this boat ride. Its a big open jet barge like I've never seen anywhere else in NA. They basically take you out and slam you into Giant Waves in the middle of the ST.L Seaway...who knew there were Giant waves there?! Anyways its one of the most fun things I can think of. And when they tell you that you will get wet just aniticpate the same experience as jumping in and out of a 6' deep pool. So double rap you valuables with bags they will give you.
Its located deep in the Old Port, you basically park near the an old shipping Pier. So just keep asking people where it is. If you're American let the Frenchies know when you ask for direction and they will be nicer to you, since they hate English Americans less than English Canadians who don't try to speak french.