1 / 4   As temperatures drop below the freezing point in northeastern China, winter swimmers braved the coldness, broke the ice and took this winter's first dive into the Songhua River. /VCG Photo

2 / 4   Winter swimming, or ice swimming, is a popular winter sport in China. /VCG Photo

3 / 4   Many winter swimming fans in China are elderly people who believe a daily dip in the cold water improves their immune system and mental strength. /VCG Photo

4 / 4   However, to people who are not used to the challenging sport, plunging directly into freezing waters can be risky and even lethal, as the icy-cold water can cause hyperventilation, hypothermia and even cardiac arrests. /VCG Photo