>>2046439 (OP)I used to do this on the Limmat, not for commute but just for fun, sitting on some inflatable donut and drinking beer which I carried in one of those watertight bags. 200% comfy would recommend.
I'd take the train to the outskirts of Zurich and get in just past the hydro plant, then float all the way to Dietikon where the next hydroelectric was. And since I lived in Dietikon I just went home afterwards.
Now I live near the Rhine which isn't really good for this, since the current is a bit slow and there's passenger ships and other obstacles. It's only worth it in a proper raft so you can row for navigation, but that's also not so fun than sitting in some inflatable. It's really the only thing I miss from living near Zurich.