Divers have removed the first bodies from the South Korean ferry that capsized nearly four days ago with 476 people on board, the coastguard has said.

"Divers broke through the window of a passenger cabin just before midnight and pulled out three bodies," a coastguard official told AFP.

All three were wearing lifejackets, the official said, adding that two were male but the gender of the third was not immediately confirmed.

The official said they were the same three bodies that had been spotted, but not retrieved, during an earlier dive.

Rescue teams planned to continue dive missions throughout the night to the ferry which capsized on Wednesday morning, he said.

The confirmed death toll from the disaster now stands at 36 with 266 people still unaccounted for.

Meanwhile the arrested captain of the ferry said he had delayed evacuating the ship because of the sea conditions and the absence of rescue ships.

Lee Joon-Seok and two of his crew were taken into police custody in the early hours of this morning, charged with negligence and failing to secure the safety of passengers in violation of maritime law.

During his police arraignment, Mr Joon-Seok was asked by TV reporters why passengers had been ordered to remain in their seats and cabins for more than 40 minutes after the ferry first sent a distress signal just before 9am on Wednesday. 

"At the time a rescue ship had not arrived. There were also no fishing boats around there for rescues or other ships to help," he said.

"The currents were very strong and water was cold at that time in the area.

"I thought that passengers would be swept far away and fall into trouble if they evacuated thoughtlessly without wearing lifejackets.

"It would have been the same even if they did wear lifejackets," he said.

Furious relatives of the hundreds of passengers still missing, most of them schoolchildren, believe many more would have escaped if they had moved to reach evacuation points before the ship listed sharply and water started flooding in.

29 people have been confirmed dead in the disaster, but 273 are still missing.

Mr Joon-Seok, 69, has confirmed that he was not at the helm of the ferry when it first ran into trouble.

"It happened as I was coming back after a quick visit to the bedroom for personal reasons," he said, denying any suggesting that he had been intoxicated.

"I did not drink," he said.

His comments offered no fresh insight into the chain of events that caused the 6,825-tonne Sewol 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, and 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 the third officer was steering when the accident happened.

Mr Joon-Seok acknowledged the charges brought against him and apologised to the victims of the disaster and their relatives.

"I sincerely apologise to people and the bereaved families for stirring up trouble," he said.

Anger after bodies found trapped

Meanwhile, angry relatives of more than 200 people missing have demanded authorities act now to raise the vessel and hit out at officials, including the country's president, as hopes of finding survivors faded.

Divers saw three bodies floating through the window of a passenger cabin today but were unable to retrieve them, the coastguard said.

Grieving parents and others gathered in a gymnasium in the port of Jindo, the centre for the rescue operation, were shown murky underwater video footage of the hull of the ship for the first time today.

It was impossible to see any bodies in the footage viewed by relatives and reporters at the site.

"Please lift the ship, so we can get the bodies out," a woman who identified herself as the mother of a child called Kang Hyuck said.

She was speaking in the gymnasium where hundreds of people have spent day and night since the ferry capsized on Wednesday.

"(President) Park Geun-hye should come here again," she said of the South Korean leader who visited the site on Thursday.