I've done internet "images" searches for muskrat, river otter, and beaver "swimming" , and I think I can rule out the muskrat, some of each of the "river otter swimming" and the "beaver swimming" look remarkably like the picture I took.
I leaned towards the otter because I know there is no beaver damn anywhere along the shoreline that this animal was swimming. I've seen him for two straight mornings, the first day it was way offshore, and stayed offshore for as long as I could still see it. Today, it was swimming the same direction but closer to shore and after passing Ellacoya it angled into the area of Scenic Drive and I was watching from the side of the road and got the pictures when it came to shore.
I hope Fish and Game gets back to me.
After looking at these image search results I'm leaning toward the beaver. The ears in the sample picture look a little more like the ears on the critter in my picture. BUT.. I can't figure out why a beaver would be in the middle of Winni swimming all the way from Samoset to a spot passed Ellacoya.
Ain't no beaver dams anywhere around that neighborhood.
Beaver
Otter