Over the past two decades, Zhang Dewu has never skipped swimming in the frozen Songhua River in Harbin, Heilongjiang province, on a winter day.

As temperatures dropped below -10 C recently in Harbin, the 70-year-old retiree became more excited about braving the cold.

He fell in love with winter swimming when he first tried it 20 years ago and immediately became a devoted enthusiast. The extreme cold and strong winds on the frozen river don't dim his enthusiasm — in fact, the extreme experience is the whole point.

Before diving into the icy river, Zhang will do some warm-up exercises, such as jogging or dousing his body with room-temperature water.

"Winter swimming makes me healthy. I seldom catch a cold," he said. "However, this exercise isn't suitable for everyone, especially for those who are suffering from heart disease, hypertension and hyperlipidemia. But I will carry on."