Full coverage: The South China Sea Issue

Chinese researchers have confirmed the world's deepest underwater sinkhole, or blue hole, is located near the Xisha Islands in the South China Sea. The blue hole is more than 300 meters deep -- and the diameter of its entrance is about 130 metres.

An aerial photo taken on July 24, 2016 shows the "Sansha Yongle Blue Hole", which was officially named by the Sansha municipal government on Sunday, in Yongle, a major coral reef in the Xisha Islands. It was confirmed on Friday by Chinese researchers that it is the world's deepest underwater sinkhole. Located at 16.31 degrees north latitude and 111.46 degrees east longitude in Yongle, the "Sansha Yongle Blue Hole" is 300.89 meters deep, surpassing the current record of 202 meters. It was traditionally known as the "Dragon Hole" and called the "eye" of the South China Sea by locals. [Photo: Chinanews.com/Luo Yunfei]

Locals call it the "eye" of the South China Sea. Traditionally known as Longdong, or "Dragon Hole", the natural marvel is located in Yongle, a major coral reef of the Xisha Islands.

Supported by the Sansha City Government of China's Hainan Province, the Sansha Ship Course Research Institute for Coral Protection recently explored the sinkhole using an underwater robot fitted with a depth sensor.

"Calibration is needed to decide its accurate depth, and an initial estimate puts its depth at about 300 meters. That is about 100 meters deeper than the Dean's Blue Hole on Long Island in the Bahamas, which is 202 meters deep. And thus, it is the deepest blue hole we know of so far," Professor Yang Zuosheng with Ocean University of China, said.

A blue hole is circular, and its name reflects the contrast in colors between the dark blue inside and the lighter shade in its surrounding waters.

They are peculiar landforms, without a doubt, but their imporance in marine research is well known.

"Research into a blue hole can provide detailed records of how the climate or water level changes over tens of thousands of years. Once we have that data, we can deduct the patten of evolution for climate change in the South China Sea, including its ecosystem, hydrological system, and its landform," Professor Yang said.

Researchers have detected more than 20 species of fish and other organisms in the upper levels of the sinkhole.

The blue hole is now officially known as "The Sansha Yongle Dragon Hole", and authorities are keen to protect, but also harness the unique qualities of the landform in the future.