DRAGON HOLE Dragon Hole is located in the Paracel Islands, also known as Xisha in Chinese, a disputed island group in the South China Sea claimed by China, Taiwan and Vietnam. World’s deepest underwater sinkhole called the “ Yongle Dragon Hole ” has been discovered by Chinese researchers in the South China Sea. Dragon Hole, or Longdong, is 987 feet (300.89 meters) deep, far deeper than the previous record holder, Dean's Blue Hole in the Bahamas. (That blue hole measures about 663 feet, or 202 m, deep.) Blue holes are water-filled sinkholes that form in carbonate rock such as limestone. Over long periods of time, the carbonate rock dissolves in the subsurface to form caves or cavities, van Hengstum told Live Science. This sinkhole, when viewed from above, has a dark blue tinge...