Squirrels can swim really far. One morning I took a friend fishing in the Mississippi River above the dam at Dubuque, IA. The river is at least two miles wide and the boat was anchored about in the middle of the river. I had dozed off in the warm morning sun, as the fishing had tapered off later in the morning. A strange noise startled me awake, and groggy eyes viewed what appeared to be a rodent crawling up my anchor line. As this strange creature was running on my gunwale, I screamed "rat! Kill it with a paddle!" To which, my conscious friend exclaimed "Relax, it's only a squirrel." The squirrel halted half between us and rested. It was exhausted, and sat there panting for several minutes.
We contemplated the fate of our new companion, now known as Skipper the squirrel. The most logical explanation was that Skipper was dislodged from his tree during the storm the night before, and had been swimming several hours in strong current. If Skipper had not found the anchor line, he most likely would have met his demise once he was carried to the dam. When it was time to go to the boat landing, Skipper clung to the transom with only his head and front paws visible for a fifteen minute ride to the boat launch. I have never seen a squirrel run to a tree as fast as Skipper did, when we reached shore.