Investigators have arrested the captain of the South Korean ferry that capsized three days ago with 476 people on board, as divers finally accessed the submerged vessel and spotted what they believed to be bodies.

Coastguard officials said captain Lee Joon-Seok and two of his crew were taken into police custody in the early hours of Saturday.

The Yonhap news agency said Lee faced five charges, ranging from criminal negligence to violation of maritime law.

Lee, 69, has been severely criticised for abandoning his ship as it sank Wednesday morning off the southwest coast while hundreds remained trapped on board, most of them children on a high school holiday trip.

Twenty-nine people have been confirmed dead in the disaster but 273 are still missing.

The coastguard revised the figures slightly overnight, citing counting errors.

As the arrests were being made, dive teams who had spent two days vainly battling powerful currents and near zero visibility, finally penetrated the lower decks of the 6825-tonne Sewol.

Briefing distraught relatives of the missing, the deputy director of the national coastguard Choi Sang-Hwan said divers had reached a lower deck passenger area around 5.50am.

“Through a window they glimpsed what appeared to be bodies but were unable to break through with the tools they had to hand,” Choi said.

He stressed that visibility was extremely poor and the divers had been unable to confirm precisely what they saw before they had to return to the surface.

Nets would be placed around the submerged ferry to prevent any bodies drifting away during the eventual recovery process, Choi said.

He added that rescue teams had not given up hope of finding survivors trapped in air pockets.

The hundreds of relatives camped out in a gymnasium in Jindo island – most of the them parents of high school students – have sharply criticised the pace of the rescue operation, accusing officials of incompetence and indifference.

“I firmly believe that the kids are alive. We need to rescue them as soon as possible. But officials are dragging their feet,” said Lee Yong-Gi, whose student son was unaccounted for.

Only 174 were rescued when the ferry sank and no new survivors have been found since Wednesday.

The unfolding tragedy was compounded by the apparent suicide Friday of the students’ high school vice principal, Kang Min-Kyu, who was seemingly overcome by guilt over having survived the sinking.

Kang, 52, was found hanging from a tree near the Jindo gymnasium. Local media said he had left a note, saying: “Surviving alone is too painful… I take full responsibility.”

More than 350 of those on board were students from Kang’s Danwon High School in Ansan city just south of Seoul.

Initial questioning of the captain has focused on what might have caused the ferry to sink.

Tracking data from the Maritime Ministry showed the vessel made a sharp turn just before sending its first distress signal.

Some experts believe a tight turn could have dislodged the heavy cargo manifest, including more than 150 vehicles, then destabilised the vessel, causing it to list heavily and then capsize.

But others suggested the turn might have been caused by a collision with a rock or other submerged object.

Investigators said Lee had handed the helm to his third officer before the accident happened.

“The captain was not in command when the accident took place,” prosecutor Park Jae-Eok told a press briefing.

Chief prosecutor Lee Seong-Yoon stressed there was no limit to the range of the investigation.

“We will make sure… those responsible are sternly held accountable,” Lee said.

Three giant, floating cranes are now at the rescue site. But regional coastguard commander Kim Soo-Hyun stressed they would not begin lifting the multi-deck ferry until they were sure there were no survivors.

“I want to be clear. There won’t be any salvage work done against the will of the families,” Kim said.

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