Swimming like a mermaid is a fantasy in many fairytales, but now it is becoming a reality and even a trend.

In 2016, Shi Ludan came up with the idea to get a diving certificate when she saw a video in which a girl swims like a mermaid without any equipment.

"That is gorgeous and I also want to master the skill," Shi said.

The 28-year-old is from Chenzhou, Hunan province. In 2016, there were not many institutions providing "mermaid" training.

"I did some research, and found a training institution in Guangzhou, Guangdong province" she said.

"Mermaid diving" is an underwater sport that incorporates swimming, diving and yoga. People wear a "mermaid tail", which weighs about 15 to 25 kilograms and perform underwater.

Professional "mermaid performers" need to keep balance and overcome the resistance and coldness underwater, using abdominal muscles and arms to control their bodies.

According to Shi, the basic course to become a "mermaid" includes book knowledge, underwater rescue and practice. Among the students she met, there are adult couples, children and retirees.

It is a two-day intensive course and costs about 2,800 yuan ($450) per person.

The "mermaid performance" also boosts the development of the whole industry, covering "mermaid tail" production and underwater photography. The styles of the costumes are also becoming more diverse such as Peking opera and animations.

Xie Yao is a professional "mermaid performer" working at Changsha Sea World.

"I will need to perform eight shows a day during the peak tourist season, and each show lasts more than 10 minutes. Being a professional performer requires underwater skills and also physical power," Xie said.

"'Mermaid diving' is becoming increasingly popular in China, and people aged 6 to 65 can learn after physical examinations.

"Being a 'mermaid' is a way of expressing the beauty of our body and also an underwater sport that not only strengthens our body but also develops a skill," Shi said.