You can swim in icy water even at eighty

Winter swimming is not just for the young. If your health allows, you can come for a swim even at eighty — with the water at 1°C, the air at −3°C and ice floating on the surface, as it was today.

Discussing it with your doctor beforehand is certainly a good idea, as it is for everyone. If you are fit to do it, there is no reason not to begin.