Hidden depths

To overcome these limitations, she had to train harder. She started practicing free sparring, which not only strengthened her leg muscles and cardiovascular system, but also improved her flexibility. In Beijing, where open water is hard to come by, she made it a habit to train regularly in swimming pools to refine her fin technique and boost her ability to hold her breath.

However, there is still a big difference between pool training and open water training. This is why many professional freedivers choose to live and train year-round in Southeast Asia. But, Ning can only spend a few months in the Philippines every year before having to return to Beijing for her family and business.

"Every family is different. I don't have to be confined to the traditional expectations of mothers always being present for their children," she said. "Besides, my daughter is proud of me. Although she may not fully understand the significance of a national record, she knows that her mom won first place in a competition."