Socotra Rock, also known as Ieodo (Hangul: 이어도; hanja: 離於島; MR: Iŏdo) or sometimes Parangdo (Hangul: 파랑도; hanja: 波浪島; MR: P'arangdo), is a submerged rock 4.6 metres (15 ft) below sea level (at low tide) located in the Yellow Sea. International maritime law stipulates that a submerged rock outside of a nation's territorial sea (generally 12 nautical miles) can not be claimed as territory by any nation. However, the rock is the subject of a maritime dispute between South Korea, China and even Japan, which considers it to lie within its exclusive economic zone. And China refers to it as Suyan Rock (Chinese: 苏岩礁; pinyin: sūyánjiāo),which means the rock(岩,yán) or reef(礁,jiāo) outside the coastal waters of Jiangsu (苏,sū,the abbreviation), while Japan refers it as the same name in Chinese character. In fact, both China and Japan use Suyan/Sogan Islet for its English name.
The rock is located 149 kilometres (80 nmi; 93 mi) southwest of Marado (just off Jeju island) in Korea. For China, Yushan Island of Zhejiang, is 287 km (178 mi) away from the rock. The rock serves as the foundation for Korean Ieodo Ocean Research Station. A Korean helipad is also located there to allow the research station to be serviced.
Both "Parangdo" and "Ieodo" are names for the mythical island which the residents of Jeju island believed housed the spirits of fishermen who perished at sea. The South Korean government has asserted a direct connection between these legends and the modern-day rock, claiming that the traditional saying that "One who sees Parangdo would never return" refers to the danger facing sailors when high waves allow the rock to break the surface. Koreans even name the studies about Ieodo as "Ieodology". Socotra Rock's Korean name was officially designated as "Ieodo" on 26 January 2001, by the Korea Institute of Geology.
1900: Socotra Rock is discovered by the British merchant vessel Socotra.
1910: Socotra Rock is surveyed by the British vessel Waterwitch, which measures the depth at less than 5.4 feet (1.6 m). Vice Admiral Archibald Day, however, wrote in his book The Admiralty Hydrograpic Service, 1795 - 1919 that this survey was 1901 not 1910.
1938: The Japanese government surveys the rock. Plans are laid for a research station, but are cut short by the outbreak of World War II.
1951: A joint team of the Republic of Korea Navy and the Korea Mountain Climbing Association reaches the rock and lowers a bronze marker bearing the legend "Ieodo, Territory of the Republic of Korea" ("대한민국 영토 이어도") onto its surface.
1963: Yuejin shipwreck: The Chinese vessel Yuejin sinks on her maiden voyage en route from Qingdao to Nagoya after being struck by an underwater object. The crew of the ship claimed to have been attacked by a torpedo, causing an international affair. It was later found that due to a navigational error by the crew, the "Yuejin" had actually struck Socotra Rock which was marked on navigational charts at the time. This was not recognized by the Korea or other neighboring countries.
1963 5.1-6.3，Shanghai Riverway Bureau fleet finds the shipwreck 1.5 nautical miles (2.8 km) southeast of Socotra Rock.
1970: South Korea's Underwater Resource Development Law was enacted, defining Socotra Rock to lie within the country's fourth mining field. This move was not recognised by the PRC.
1995-2001: the Republic of Korea builds the Ieodo Ocean Research Station on Socotra Rock despite the objections from People's Republic of China. Several overflights of the area have since been made by the PRC surveillance aircraft.
2001: the Korea Institute of Geology officially designates the rock as "Ieodo" on 26 January 2001.
In September 2006, the Chinese Foreign Ministry spokesman Qin Gang (秦刚) told reporters that China objects to South Korea's "unilateral" activities in the region, referring to Korean science observation facilities on this reef island, which the Chinese Foreign Ministry spokesman has claimed to be "illegal". However, Chinese reports notes that Qin Gang said the two countries never had a "territorial dispute", not mentioning any islands. In 2013, the PRC clarified their position by stating that China had no dispute with Korea on the issue.