Dragon Hole

Dragon Hole, also known as Yongle Blue Hole named after the third Ming emperor, is the deepest known blue hole in the world at 300.89 metres (987.2 ft) deep. It is located about 9 kilometres (5.6 mi) north of Drummond Island in the Paracel Islands. Blue holes generate a distinctive blue colour when seen from above and are typically only a few dozen meters deep.

The local fishermen call it the "eye" of the South China Sea, and according to legend it is where the Monkey King, depicted in the novel Journey to the West, found his golden cudgel.

Dragon Hole is about 25 metres (82 ft) deeper than The Taam ja' Blue Hole off the Eastern coast of Mexico and 100 metres (330 ft) deeper than Dean's Blue Hole in the Bahamas. There are several fresh water sinkholes on land that are deeper than Dragon Hole. These include Mexico's Zacatón (335 metres (1,099 ft)), Pozzo del Merro in Italy (392 metres (1,286 ft)) and Hranice abyss in the Czech Republic (404 metres (1,325 ft)).

The Sansha Yongle Blue hole was created around the same time as the surrounding South China Sea islands. Blue holes can be formed in a number of ways. The most common is melting ice structures in the surface resulting in large pits where ice once was. Blue holes may also be formed after a disruption in the surface of the ocean floor by tectonic shifts that result in the settlement of sand and debris (Emery, 1962). The Blue Hole in Belize was once a dry land cave; its present form is a result of sea level rise and subsequent roof collapse.