Trouble with a capital B

On Sunday last, Jim saw a moose swimming across the lake from right to left, east to west. I was driving around somewhere. He took no pictures. He has seen three so far. I have not seen such a thing. He says they moose paddle.

This morning I debate whether this swimmer is a beaver or a very large muskrat. The teeth are much bigger in a beaver. And who ever heard of a muskrat having to be trapped as a nuisance because of cutting down the trees along the shoreline?

I'm hoping that beavers do not like metal floats or cables or the pressure treated wood of a floating dock.
When swimming, a beaver's tail goes up and down and a muskrat's tail goes side to side. According to the moose spotter.