Four boys and two girls from Dongguan, Guangdong province, aged from 11 to 15, swam across the Qiongzhou Strait in South China on Aug 21, covering a distance of about 20 kilometers.

They hit the water in Haikou, Hainan province, at 4:30 am and wrapped up the journey in Zhanjiang, Guangdong province, at 12:30 pm.

Thirteen-year-old Zhao Ziqian and Zhao Qinman — brother and sister twins — finished first, in 6 hours and 24 minutes.

"Our goal is to lift their physical strength, character and personality through swimming. There are some potential dangers, but most of them can be prevented by the choice of good weather and sea conditions," said Chen Suwei, the swimmers' coach.

"We did a lot of training before, and they had a highly reliable team to safeguard them," Chen said.

Wang Han contributed to this story.