Japan, China, Korea? Yes, Maybe lack of real estate makes modern swimming pools rare.
Indonesia, Thailand, Vietnam, India, Sri Lanka? People swim in rivers, lakes and oceans, especiallly at the end of the work day.
Depends what you mean by Asia.
It’s pretty common in Latin America as well afaik. I would guess it has to do at least partly with whether it’s taught in PT at school. Also public pools are not a thing in many places and not many gyms have pools.
Water brain eatin ameoba were a thing, are