Currently the deepest known underwater sinkhole (blue hole) is Dragon Hole – 300.89 m deep hole in a shallow shoal in Paracel Islands.

This sinkhole has been known to local fishers for centuries. According to local legends, this is the eye of the South China Sea and here the Monkey King found his golden mace.

In 2015 – 2016 a team of Chinese researchers (Sansha Ship Course Research Institute for Coral Protection) explored this unusual place, robot "Video Ray Pro 4" reached the full depth of the sinkhole.

Upper part of the sinkhole is rich with sea life but at the approximate depth of 100 m starts a layer of oxygen-free water which, most likely, is devoid of life.

Dragon Hole has formed in the massive Miocene deposits of limestone which are more than 1200 m thick (1). It is not quite clear how such a deep underwater sinkhole was created.

Currently (end of 2016) fishing and tourism in this area has been prohibited.

Dragon Hole is included in the following list:

Largest and most impressive sinkholes of the world
Largest and most impressive sinkholes of the world


  1. Shiguo Wu, Xinyuan Zhang, Zhen Yang, Tuoyu Wu, Jinwei Gao, and Dawei Wang (2016). Spatial and temporal evolution of Cenozoic carbonate platforms on the continental margins of the South China Sea: Response to opening of the ocean basin. SEG Interpretation, August 2016. doi: 10.1190/INT-2015-0162.1
  2. China Exclusive: South China Sea “blue hole” declared world’s deepest. Xinhua, 23 July 2016. Accessed on 22nd December 2016.
Dragon Hole on the map
[travelers-map height=320px this_post=true init_maxzoom=9]
Location, GPS coordinates: 16.5250 N 111.7681 E
Categories: Sinkholes, Geographical extremes
Values: Geology, Visual
Rating: 4 out of 10 stars
Where is located? Asia, China (disputed), Paracel Islands, in shallow bank to the east from Pattle Island, near Discovery Reef
Name in Chinese: 三沙永乐龙洞 (Longdong)
Alternate names: Sansha Yongle Blue Hole
Depth: 300.89 m

Landmarks of China

Karst landscape at Li River, China
Karst landscape at Li River / , Flickr / CC BY-SA 2.0
China has got it all – more than one billion people, large area, great and very long history, very distinct and at the same time – very diverse cultures, great and varied nature.


Great Blue Hole, Belize
Great Blue Hole / Eric Pheterson, Flickr / CC BY 2.0
Category includes outstanding sinkholes – large natural depressions or holes, which for most part represent collapsed caves.

Recommended books

Caves: Exploring Hidden Realms

A companion volume to the new IMAX film offers a sumptuously illustrated, close-up look at the world’s great cave environments, capturing the wonders and perils of caving and describing the unique characteristics of these underground habitats.

Karst in China: Its Geomorphology and Environment

This is the first study of the karst areas of China to be carried out by a Western geomorphologist, and almost all the sources are from Chinese works, as yet unpublished in the West. Karst areas are sensitive to environmental influences and Chinese attempts to deal with these are discussed here, as are Chinese methods of studying karst since they differ somewhat from those in the West.

1 2 votes
Article Rating
Notify of
Inline Feedbacks
View all comments