Definitely a possibility. I've looked at videos of swimming river otters, muskrat, and mink, and none of them really look like what I saw; all the videos show the critter higher in the water than what I saw. What I saw was just the nose and eyes, and the wake. Couldn't even get a sense of how big the thing was.
I'm inclined toward mink because I've seen mink in the area (well, ten miles away) and I haven't seen otter or muskrat (that I know of).
Or in my case city rats! Planned drive today for appointments - good thing, 7F