1. Eating pilose antler has obvious effect. There is also eating mutton, but eating mutton is not afraid of cold for a while, and eating velvet for a while.

Taking a cold bath in winter is also very useful. Not only not afraid of cold, but also less cold.

Wear short sleeves in winter and stubbornly say "no". No, no. . . . Cold. . . "

4. Grind the leather thicker and use it as leather.

5. gain weight and let subcutaneous fat help you keep out the cold. In other words, wear a leather coat above and a cotton-padded jacket below.

Hey hey, I'm kidding, but the first two points are really effective. What's wrong with learning to swim at the age of 2/kloc-0? You don't have to learn from children. Just make a girlfriend who can swim and teach you, or find a friend to teach you.

Why do you have to wear short sleeves in winter? Learn from foreigners? They have been trained by cold water immersion in winter since childhood. Besides, as far as I know, most of them put up with it.