The "Dragon Hole", the world's deepest blue hole is 300.89 metres deep

Chinese researchers have confirmed the world's deepest underwater sinkhole, or blue hole, at China's Xisha Islands in the South China Sea.

The blue hole is 300.89 meters deep, surpassing the current record of 202 meters, the researchers confirmed Friday.

The hole, traditionally known as Longdong, or "Dragon Hole," is located at 16.31 degrees north latitude and 111.46 degrees east longitude in Yongle, a major coral reef in the Xisha Islands.

Locals call it the "eye" of the South China Sea. In some local fishermen's interpretations of the 16th-century Chinese Classic "Journey to the West," the sinkhole is the site where the hero's weapon, a golden cudgel, originates.

The latest exploration project, which lasted from August 2015 until June, found the hole is 300.89 meters deep with a 130-meter-diameter-wide entrance, said Fu Liang, head of the Sansha Ship Course Research Institute for Coral Protection, at a conference on Friday.

Supported by the Sansha City Government in south China's island province of Hainan, the institute explored the sinkhole using the "VideoRay Pro 4" underwater robot carrying a depth sensor.

Researchers with the institute have also found more than 20 fish species and other marine organisms at the upper level of the sinkhole. The blue hole is almost oxygen free below 100 meters, meaning life is unlikely.

The findings have been recognized by an expert panel led by Meng Wei, an academician with the Chinese Academy of Engineering.

A blue hole is a roughly circular sinkhole. The name reflects the color contrast between the dark blue inside the hole compared with the light blue waters surrounding it.

Previously, the 202-meter-deep Dean's Blue Hole on Long Island in the Bahamas was considered the world's deepest known blue hole with an underwater entrance.

Panel leader Meng said blue holes are peculiar marine landforms that are important for marine research and the construction of marine projects.

The panel has advised including protection and exploitation of the blue hole in the five-year plan at the country, provincial or city level.

Xu Zhifei, vice mayor of Sansha City, said the city has drafted measures to protect, study and exploit the blue hole.

"We will strive to protect the natural legacy left by the Earth," he said.

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