Professional tae kwon do teacher Lee Jun-ho took up scuba diving eight years ago as a fun hobby.
It was never meant to lead him to the black, nightmarish world of a submerged ferry looking for the bloated bodies of hundreds of schoolchildren.
Last Wednesday, Lee, 41, was preparing for another day teaching children at his school in Gimhae, near the port city of Busan, when he heard reports of an unfolding ferry disaster off the southwest coast.
As the scale of the tragedy became apparent, Lee, who qualified as a diving instructor in 2008, packed his dive gear in his car and drove 256 kilometres to Jindo island, where a rescue effort was taking shape.
There he found scores of other civilian divers who had come individually or with their clubs to volunteer in the search for survivors in the submerged ferry, which was carrying 476 people.
"I have two young sons of my own," Lee said. "The thought of all those schoolchildren trapped or worse was just unbearable, and I thought I had a duty to try and help save them," he said.
More than 500 divers, including elite South Korean navy SEALs, have been taking part in the rescue efforts, many of them civilian divers with no real experience of such work. "It was a bit of a mess at the beginning," Lee acknowledged, with military, coastguard and civilian dive teams struggling to co-ordinate their efforts.
Most feel the civilian divers have proved their worth; it was a team of civilian divers who retrieved the first bodies from inside the ferry on Sunday. "The mood changed a lot after that," Lee said, with many of the amateurs leaving once it became clear there were no survivors to be rescued. But Lee stayed on. "I'm proud of what we did and are still doing here."