Believe it or not, the swimmers are senior citizens of 60 years and older. During one of the flights, I came across an article about the benefits of swimming in cold water. The article reported that older coldwater swimmers enjoy a healthy sex life, better than their age indicates! You learn something everyday. The swimming pool? What swimming pool? It was just cut out section of the solidly frozen Songhua river. Do you see the edge of the "pool" :)?