During regular submersion 53 -year-old diver, surnamed Li lost consciousness.
At 07.12 am local time he was rushed to a nearby hospital in the port of Mokpo in the southwest of the country, but the doctors could not do anything and soon announced that he had died.
Communication with lifeguard, who worked for the company Undine Marine Industries, was lost five minutes after his dive to a depth of 25 meters.
262 dead bodies were found for 19 days of search and rescue operations on the sunken ferry. Another 40 people are unaccounted for, said the government's operational headquarters on the island of Chindo.