Ieodo is a submerged rock within a Korea's territorial line in the East Sea with its most shallow part about 4.6m below the sea level. Based on 40m in depth, it stretches about 600m north-south and 750m east-west from its top while it makes steep slopes in south and east and rather gentle slopes in north and west.
Ieodo is known as an island of fantasy and nirvana in the folk tale of Jeju-do residents. The folk tale goes that anyone seeing this land cannot return alive. That might be because fishermen could see Ieodo Rock only when the waves hit over 10m high, which didn't allow them for safe return to their home.
Ieodo was first discovered in 1900 by Socotra, the British commercial ship, and thereafter called as the Socotra Rock named after the ship. Then in 1901, the British Navy surveying ship of 'Water Witch' conducted survey on Ieodo and confirmed it as a submerged rock about 5.4m in depth.
In 1938, Japan planned to build an artificial structure with 15m in diameter and 35m above the sea level in Ieodo in order to establish submarine ferry relay and lighthouse facilities, but failed because the Pacific War broke out.
It was 1951 when the Korean public began to recognize Ieodo. At that time, the Korean Alpine Club and the Korean Navy conducted a joint investigation into Ieodo and sank a copper plate engraving 'IEODO' onto the rock under the sea after identifying the black rock in high waves with their bare eyes.
Then in 1984, Jeju University and KBS Parang-do academic research team made a joint research to confirm its location. In 1986, the Office of Hydrographic Affairs (current NORI) surveying ship measured its depth as 4.6m.
The first structure on Ieodo was the Ieodo light buoy (navignTunal mark buoy playing a role like unattended lighthouse indicating dangerous places for voyage of ships) constructed by the Korea Maritime and Port Authority in 1987, which was announced internationally.
Since Ieodo is located within the waters closer to Korea than other neighbouring countries, it will be under Korea's maritime jurisdiction according to the Middle Line principle which is applied to the determination of EEZ.