A newly discovered blue hole in Huangyan Dao has been identified as China's first known coral reef-formed blue hole. With its opening covering nearly 1,500 square meters, the blue hole reaches a depth of 16.6 meters and is estimated to be at least 3,200 years old. Researchers say the blue hole and its surrounding waters support rich biodiversity, offering new insights into coral reef evolution and marine ecosystems in the South China Sea.■
