Usually here if it's winter the water is ice and all I hope is it's thick enough to support us. But I realize current and wave action and salt water would postpone freezing. For me I think, what will the dog do after? IS there still enough walk left for him to run around and warm up? Did I plan something on the way home meaning he'll have to lie in the car and wait, wet, for me? For the first, yes swim. For the second, no. And by the way, cold tail does not only happen in cold water. It was very warm when Oban got it. He was retrieving into the pond and diving off the high bank. His tail was going SMACK when he hit the water. I'm told it's fairly common in dock diving. Any unusual tail action can strain those muscles but of course cold water is a common factor too. LOL, I have to comment on rolling in sand too. You would not believe how rolling in snow also helps dry them off.