River otter
This week a River Otter (Lontra canadensis) appeared in the lake behind our house. It alternated rapidly swimming around on the surface and diving for extended periods. I was very busy moving around the house trying to get a picture of it through the windows while trying to keep the many trees between the house and the lake out of the picture. After about 10 minutes the otter disappeared for good, and the only photograph I managed to get shows it heading away.
We have seen otters in the lake quite a few times since we moved here. I do not believe they live in the lake, but rather they patrol up and down Hawks Creek, which is adjacent to the lake. Occasionally, they decide to visit the lake on a fishing expedition. In one case an otter climbed up on our boat dock for an inspection, and I have seen them on the bank next to the lake several times. We also have beavers in the lake, but they swim more slowly and in a direct and stately fashion.