The confirmed death toll increased to 20 yesterday as strong currents held up plans to pump oxygen into the Sewol to help any survivors stay alive.
The captain, Lee Joon-seok, 69, was under investigation in the city of Mokpo in the south of the country, where the inquiry is based, amid unconfirmed reports he was among the first to jump to safety after the ferry started to list on to its side on Wednesday.
It is thought an evacuation order may not have been broadcast to passengers who had been told to stay put. The cause of the disaster remains unclear, but investigators said the ferry was off its usual course and had been buffeted by winds which dislodged containers on deck.
Kim Han-sik, president of Chonghaejin Marine, which owns the ferry, had to be supported by two men as he made an apology for the disaster to the victims and their families.
He said: “I committed a sin punishable by death. I am sorry. I am sorry.”
Most of the missing are teenagers, among 325 high school pupils and 15 staff en route from near Seoul to a field trip on the resort island of Jeju, south of the mainland. The 480ft ferry was carrying 475 people – 445 passengers and 30 crew. A total of 179 have been rescued so far.
The confirmed dead include at least five students, two teachers and a crew member.
The ferry sank within two hours, with only two life rafts being successfully launched.
David Jardine-Smith, secretary of the International Maritime Rescue Federation, said hope rested on whether those trapped inside had been able to find air pockets.
He said: “It is not impossible that people have survived but, tragically, it’s very unlikely that many will have done.”
Rescue teams yesterday hammered on the hull of the upturned vessel, hoping for a response from anyone trapped inside, but heard nothing.
Mr Jardine-Smith said conditions were extremely difficult.
He said: “There is a lot of current and silt in the water, which means visibility is very poor and the divers are basically feeling their way around.”
Search firm Web Solus is providing an underwater drone to examine the interior of the vessel in an attempt to find survivors.
Operator Ko Se-jin said: “Families and rescuers have been just looking at the surface of the sea. We have to move fast and at least see some of the vessel under the water.”
Some survivors said crew told them to stay onboard right up to the point that the ship was going down.
Student Choi Min-ji said: “It is outrageous they didn’t tell people to get out. They kept saying, ‘Stay put’, even when the water was coming in. I almost got trapped too and barely came out alive.”
Businessman Koo Bon-hee, 36, said many people were trapped inside unable to break the windows. He said he had wanted to escape earlier but did not because of the announcement for passengers to stay put.
He said: “The rescue wasn’t done well. We were wearing life jackets. We had time. If people had jumped into the water they could have been rescued. But we were told not to go out.”
However, another survivor, Lee Tae-ju, 68, said some people believed the order to stay put sounded reasonable at the time.
He said: “The ship was listing sharply, so I would have tried to tell people to stay put if I were them, just to keep calm. What can you do? In any case, the ship was listing so sharply it would have been almost impossible to get out.”
A crew member said the evacuation order may not have been passed to passengers because of chaos and confusion on the bridge as officers battled to stabilise the vessel.
Oh Yong-seok, 58, said passengers had been told to put on life jackets, but the evacuation instruction from the captain
30 minutes later may not have been passed on.
He said by then it was impossible for crew to help the passengers because the ship was listing at an impossibly acute angle.
The crewman, who escaped with some 12 colleagues, said: “We couldn’t even move one step. The slope was too big.”
Video shot by truck driver Kim Dong-soo showed the vessel listing severely as people in life jackets clung to the side of the ship to keep from sliding away.
A loudspeaker announcement can be heard telling passengers to stay in their quarters.
Three vessels with cranes on board are due to arrive to help with the rescue and salvage the ship.