"Also, free-diving is more flexible and is like communicating between one's mind and body. You have to be out of the water by the time you ran out of breath."

Chen also urges environmental awareness among tourists, adding that when she sees plastic bags and tin cans in the ocean she takes them out of the water and disposes of them responsibly.

Official data shows that in 2017, the number of Chinese tourists visiting the Philippines was about 969,000, an increase of about 43.4 percent over 2016, making China the second-largest source of tourists for the country.

The Philippines is now targeting 2 million Chinese tourists annually.