Emergency services are continuing to search for nearly 300 people missing after a ferry carrying more than 470 people sank off SouthKorea.
Officials say 179 people have been rescued. Most of the passengers were students from the same high school.
Bad weather and strong currents have hampered military divers' efforts to enter the ship, where it is thought many were trapped.
At least nine people are confirmed to have died, with dozens more injured.
The vessel was travelling from Incheon port, in the north-west, to the southern resort island of Jeju.
It is not yet clear what caused the ship to list at a severe angle and flip over, leaving only a small part of its hull visible above water.
The captain was being questioned, Yonhap news agency reported. "I am really sorry and deeply ashamed. I don't know what to say," Lee Joon-seok was shown saying on television.Yonhap said the nine dead include four 17-year-old students and a 25-year-old teacher as well as a 22-year-old female crew member. Identities of the other three were not immediately known.
The latest figures say 475 people were on board, with 287 still unaccounted for. Figures issued by the government have changed several times, prompting criticism.
South Korean President Park Geun-hye on Thursday visited the scene of the disaster, as rescue work continued.
Strong currents Efforts are concentrated on the ship, which sank in about 30m (100ft) of water.
"We carried out underwater searches five times from midnight until early in the morning, but strong currents and the murky water pose tremendous obstacles," said Kang Byung-kyu, minister for security and public administration.
One senior emergency official was quoted as saying it was unlikely the remaining passengers would be found alive.
The US Navy has sent an amphibious assault ship, the USS Bonhomme Richard, to assist with the search.
Captain Joey Tynch told the BBC conditions were difficult.
"We found ourselves in challenging weather conditions today - very low cloud ceilings and reduced visibility and rain, and we're working a search area around the site in close co-ordination with the South Korean on-scene commander," he said.
Two cranes are being sent to raise the vessel, with both expected to arrive on Friday.
'Screaming and scrambling' The ferry sent a distress call at around 09:00 local time (00:00 GMT) on Wednesday, about 20km (12 miles) off the island of Byungpoong. It sank within two hours, reports said.
At least 325 of the passengers on board the ship were students from Danwon high school in Ansan, near the capital, Seoul.
The students, aged 16 and 17, were heading on a field trip to Jeju island with about 15 teachers.