They say low water is 5 ft. Here's what the official site says. We plan to take our 53 through there in 2007, but it may depend on drought or rain that year.
4. My sailboat boat draws 5 ft. Is there one section that is that depth or shall I be nudging bottom all the way? We usually caution any boater with draught of 5 feet or greater about the possible "bumping" of obstacles in areas such as Canal Lake. Boaters with draught like this will need to sign a waiver at the first lock encountered. So many factors can affect draught such as where the rating is for eg. salt water etc., whether loaded or not, full of fuel or not, under power or not, etc. that we usually like to get a call from the prospective boater before the trip to ensure he/she understands the possible trouble. A low water problem would be announced and quite evident as caused by drought conditions.
At 5 feet we would expect the boater could safely pass through the route. Floating debris may at times get pulled up from the bottom in some shallow areas when one boat is following another closely. The second boat may experience a "bump" at such a time, but suffer little damage. The area outside the waterway in the approach from Severn Sound has been affected in the last few years due to the low levels of Georgian Bay and Lake Huron. Closer to the time of the trip the level of Lake Huron will be better known to assess this hazard too.
I recommend a call to Mike Jamieson (705) 750-4937 a few weeks at most prior to the trip.