On July 24, 2016 (Lunar calendar June 21, 2016), Sansha discovered the world's deepest ocean blue hole. The picture shows an aerial picture of Longdong. According to China News Agency Sansha on July 24, 2016 (reporter Prince Qian) After on-site investigation by experts, the Sansha Municipal Government officially named the ocean blue hole of Yongle Atoll in the Xisha Islands as "Sansha Yongle Dragon Cave" (SanshaYongleBlueHole) on the afternoon of the 24th. It was confirmed to be the deepest known ocean blue hole in the world. It is located in the reef of Jinqing Island and Shiyu in Yongle Atoll, Xisha Islands, Sansha City, with a depth of 300.89 meters. The address coordinates are 16 ° 31 ¡ä 30 ° north latitude and 111 ° 46 ¡ä 05 ° east longitude. Ocean blue holes are a rare natural and geographical phenomenon on the earth. When viewed from the sea surface, blue holes show a different dark blue color from the surrounding waters, and a huge deep hole is formed on the seabed, which is hailed by scientists as "the last legacy of the earth to retain the secrets of the universe to mankind". Previously, the world's proven ocean blue hole depth rankings were: Deans Blue Hole on Long Island, Bahamas (202 meters), Hadab Blue Hole in Egypt (130 meters), Belize Blue Hole in Honduras (123 meters), Gozo Blue Hole in Malta (60 meters), and the depth of Yongle Blue Hole in Xisha greatly broke the new record of the world's ocean blue hole. "Sansha Yongle Dragon Cave" has a long-standing legend. Hainan fishermen say that this place is where the Dinghai God Needle is located. Sun Wukong pulled out the Dinghai God Needle to make a ruyi golden hoop, leaving an unfathomable dragon cave; some fishermen say that the dragon cave is the eye of the South China Sea, hiding the treasure of Zhenhai in the South China Sea. From August 2015 to June 2016, the Xisha Trail Research Institute used sonar side-scanning equipment, electronic counting plumb, deep-sea current meter, deep-sea water quality analyzer, underwater robot, underwater photographic camera equipment and other equipment, and used a combination of scientific equipment detection and artificial diving observation and measurement to successfully determine the depth and basic form of the blue hole. The expert group led by Meng Wei, an academician of the Chinese Academy of Engineering, found the exploration results credible. After exploration, the Xisha Yongle Blue Cave is basically a vertical cave. The diameter of the blue hole is 130 meters, and the diameter of the bottom of the cave is about 36 meters. The connection between the blue hole and the outer sea has not been observed, and the water body in the cave has no obvious flow. Through visual inspection, more than 20 kinds of fish and other marine organisms similar to the surrounding waters were found in the upper layer of the cave. The Sansha Municipal Government pointed out that the "Sansha Yongle Dragon Cave" has extremely high scientific research value and historical and cultural value, and is a true witness to the long-term adherence of the Chinese government and people to ecological and environmental protection.