Three bodies were found early Saturday within passenger cabins of a South Korean passenger ferry that capsized three days ago, as the captain was arrested and charged with negligence.

The bodies were sighted at around 5:50 a.m. (2050 GMT Friday) on the fourth floor of the five-story vessel by private divers, the first discovery within the hull since the 6,825-ton "Sewol" sank off Jindo Island near the southwestern tip of South Korea with 476 people on board.

The divers tried to break open the doors, but failed due to limited diving time and floating obstacles.

Two coast guard divers tried to pry their way into passenger compartments on the third floor at 11:08 p.m. (1408 GMT) Friday, but were also prevented by various obstacles.

The coast guard said they had not received any messages from within the cabins.

The third and fourth floors are composed of passenger cabins, and there are freight compartments on the second floor and a dining room on the first. Divers succeeded in reaching the first and second floors on Friday.

Around 87 passengers stayed in the cabins on the third floor, with 353 put up on the fourth floor and seven on the fifth. 29 people have been confirmed dead in the disaster, with 273 still missing, including four Chinese citizens.

Also on Saturday, investigators arrested the 69-year-old captain and two of his crew, charging them with negligence and failing to secure the safety of passengers in violation of maritime law.

Questioned why passengers had been ordered not to move for more than 40 minutes after the ship first floundered, captain Lee Joon-Seok said it was a safety measure to prevent passengers being "swept" away.

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

"The currents were very strong and the 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."

Lee also confirmed he was not at the helm when the ship ran into trouble, and was returning to the bridge from his cabin.

He said, "I am sorry to the people of South Korea for causing a disturbance and I bow my head in apology to the families of the victims."

Angry relatives of the missing, mostly high school students on a four-day field trip, demanded authorities act now to raise the vessel and criticized officials after learning about the discovery of bodies.

Gathering in a gymnasium at the port of Jindo, the rescue center for the operation, they were shown underwater video footage of the hull on Saturday for the first time.

On Saturday, 652 coast guard, military and private divers were expected to try to enter into the hull 40 times, while 176 rescue ships and 28 airplanes were deployed to search waters near the submerged ferry.

Three giant, floating cranes are now at the rescue site, but coast guard officials stressed they would not begin lifting the multi-deck ferry until they were sure there were no survivors inside.

More than 20 ships have been cleaning up waters near as oil leaked out of the capsized ship, the coast guard said.

The ship departed from South Korea's western port city of Incheon Tuesday night for the southern resort island of Jeju. Among the 174 rescued, 75 were students from the Danwon High School in Ansan, a Seoul suburb.