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.
I don't think the dock diving is as big an issue as just a lot of swimming. Our first Lab got it a couple of times when she swam several hours. Labs tails go back and forth while they swim. Cold tail will usually resolve itself in a few days, and with Ginger it never seemed to bother her, so much as to make her look kind of sad with her tail down. I know that with some dogs it seems to be really painful. Tilly was a dock dog wanna be, but I don't think she ever got cold tail, certainly not when she was dock diving. Cooper has not experienced it yet, though she is probably the strongest swimmer of all our Labs.
We condition for cold water. Duggan gets a swim as the seasons change so he doesn’t go straight from warm summer water to frigid winter water during the hunting season.