Hahaha. There are people who regularly swim in the water in winter, and we call them walruses. It's also popular in Sweden and Finland.
But on January 21, Epiphany, it is believed that no one will get sick after swimming in icy water. But personally, I don't do that. Although after a hot bath, when I was young, I rolled in the snow and swam in an ice hole on the lake. I won't do that now either, I need some training.