Dragon Blue Hole is deepest blue hole in the world. It is 987 ft deep sinkhole, with a distinctive blue color water when seen from above. Almost 330 ft deeper than Dean’s Blue. This is located 25 KM from south of Discovery Reef in Paracel Islands.
It is famous as “eye” of the South China Sea. A stark contrast to the otherwise aqua waters that surround striking and beautiful formations of underwater entrances and extend below sea level, mirroring the appearance of a sinkhole.
Moreover, there are several fresh water sinkholes on planet earth, that are deeper than Dragon Hole. These include Mexico's Zacatón 1,099 ft, Pozzo del Merro in Italy 1,286 ft, and Hranice abyss in the Czech Republic 1,325 ft.