When my son came home from school, I saw a note in the contact book that said, "There will be a swimming lesson tomorrow, but you don't need to bring a swimsuit; you need to bring your usual long-sleeved top and pants, and a two-liter Porter bottle. When I asked my son, he realized that the school was having a "swimsuit" class, which means swimming with clothes on. In Japan, from the first grade of elementary school to the third grade of middle school, swimming lessons are held twice a week during summer physical education classes. Even in the Hokkaido public elementary school where my husband went to school in his childhood, the temperature in winter went down to more than 10 degrees below zero.