Using the key on GoBotany, and leaning heavily on the range maps there (i.e. ignoring any thing not shown to occur in Norfolk County).
1b. Flowers with only an adaxial nectary (all of the possibilities that would also have an abaxial nectary can be ruled out on stamen number or bract color)
12b. Filaments glabrous throughout.
24b. Aments coaetaneous. This one is not obvious, but I believe it is the right choice in the key. The choices for precocious aments (S. humilis, S. occidentalis, and S. viminalis) are also ruled out by the color of the branches)
29b. Floral bracts brown or black
The key then goes to leaf characteristics, which I did not observe. But the other choices (S. pedicellaris and S. viminalis) are ruled out on habitat and branch color.
Floating tuber thing in small shallow pond with lots of aquatic plants.