Canals are tough because the maintenance of the canal is much harder, and the flow of the canal also makes things tricky. Dr. Brandi McKuin has done some work here, looks like the best way to do this is to hang the panels suspended on cables over the canals, but that requires a lot of steel and is thus fairly expensive. I don't think we've cracked that nut yet...

Floating is overwhelmingly better, because cold panels are more efficient than dry ones.