Since it's hard to gauge the critter's size in this photo and since the log (Dam log! ... Hee hee, beaver humor) is blocking the view of it's tail, it's impossible to tell whether it's a beaver or muskrat.
Fairly certain it's not a duck, though! :)
Thanks for sharing the photograph, Jeff. There's nothing like a good rodent mystery to stop and make you think and break up your day. The downside ... I now want to KNOW which it is!!!