The City of Sarnia is warning residents and boaters to watch for underwater structures along its shoreline.
Some seawalls, piles, groynes and docks are submerged under high water in Lake Huron and the St. Clair River, posing a hazard to boaters and swimmers alike, the city says.
The U.S. Army Corps of Engineers, which tracks daily water levels in the Great Lakes, points to persistent wet conditions and high outflows for the exceptionally high water levels this year.
Lake Huron is 31 inches above normal for this time of year.
The St. Clair River is 33 inches higher than normal, and four inches higher than the July record set in 1986.
The Corp is predicting water levels to drop a bit in August.