Answer: South China Sea
Notes: The Sansha Yongle Blue Hole, known as the Dragon Hole, is a massive underwater sinkhole in the South China Sea studied for over a decade. Blue holes are deep, steep underwater cavities formed in limestone areas and later filled by rising sea levels. Dragon Hole is the deepest known underwater sinkhole in the world at about 301.19 meters, deeper than Dean’s Blue Hole in the Bahamas. It lies around 25 kilometers from Discovery Reef and is called the “eye” of the South China Sea by local fishermen. The hole is almost vertical, with 130 meters width at the surface and 36 meters at the bottom.
