China releases findings on blue hole at Huangyan Dao

China unveils findings on the country's first known blue hole formed by coral reefs at Huangyan Dao.

The blue hole covers an opening area of around 1,491.7 ㎡ with a maximum diameter of 56.3 m and a depth of 16.6 m.

The blue hole came into being at least 3,200 years ago.