JINDO, South Korea (AFP) - Providing a DNA sample marked an emotional watershed for Ms Han Mi Ok - a heart-wrenching acceptance that she was unlikely to ever see her child alive again.
Her son Song Kang Hyun was one of 325 high school on board the ferry Sewol when it capsized and sank more than three days ago en route to the southern resort island of Jeju.
While some were rescued, hundreds remained unaccounted for and, for parents like Ms Han, it was becoming harder to keep any sort of grip on the slim hope that they were alive in an air pocket somewhere in the submerged vessel.
The painful transition from hope to acceptance was played out in a green and white tent erected close to the gymnasium on Jindo island where hundreds of distraught relatives have been sheltering since the ferry went down Wednesday morning.
Inside the tent, two tables were manned by four men from the South Korean coastguard's Crime Scene Investigation (CSI) unit.
Their task was to take DNA samples from any relatives willing to provide them, in order to facilitate eventual identification of bodies recovered from the 6,825-tonne Sewol.
Twenty-nine people have been confirmed dead in the disaster, but 273 are still missing.
"Up until yesterday, I was still hanging on to some hope," Ms Han told AFP on Saturday.
"But today I am bracing myself for the worst," she said, before entering the tent where she swabbed her mouth with a cotton bud and handed it to the CSI team.
"Even if my son were alive, I don't seen how he could ever be reached in time," she said afterwards.
After two days vainly battling powerful currents and near zero visibility, dive teams finally penetrated the submerged ferry's passenger decks on Saturday morning.
The coastguard said civilian divers had spotted three bodies through a window, but had been unable to break through the glass to retrieve them.
Ms Han was accompanied by her teenage daughter who had not gone to the same Danwon High School in Ansan, south of Seoul, that her brother and the other students on the Sewol attended.
"I suppose I should be grateful for that," Ms Han said.
"If they had been in the same school I might have lost them both."
She was very much in the minority in having her DNA tested, with most parents still not ready to accept the conclusions associated with such a step.
Some reacted angrily to even being asked if they wanted to provide a sample.
"Of course not! How would that help?!," shouted one mother.
"We've collected some samples, but I'm not going to say how many," said one of the CIS officers before declining to discuss the issue any further.