There is still no official explanation for the sinking, although the government has launched a formal inquiry.
Hundreds of South and North Koreans have been reunited for the first time in six decades after being separated by the Korean War.
North Korea has marked the 60th anniversary of the truce that ended the Korean War with a massive celebration in the capital Pyongyang.
Police said a high school vice principle rescued from the South Korean ferry that sunk has been found hanged, the Associated Press reports.
A diver tasked with getting information from the sunken ferry has told relatives that they "cannot even see the ship's white colour".
Diver Kim Chun-il said that two divers had to return to the surface when an air pump stopped and said strong tides were impeding the rescue and that the divers are only "touching the hull with their hands."
Rescuers have pumped air into the vessel, but divers have not yet entered areas of the ship where many of the missing are believed to be.
South Korean families and friends of missing students aboard a sunken ferry await any news on survivors at Danwon High School, as the search continues for about 270 missing passengers
Many have slept in the gymnasium throughout the ordeal.
Video shown below in South Korean:
One 21 year old alumni Kim Yankg-Eun said on the phone:
"She is such a caring girl, so she must have asked other people to evacuate first leaving herself behind. She must be inside the ship waiting for rescuers with her friends"
Four seaborne cranes have arrived to salvage the sunken South Korean ferry as the search continues for 270 missing passengers.
Rescue and recovery attempts were continuing on Friday, but the work was expected to be slow.
The captain of the South Korean ferry who was not at he the helm as it capsized and evacuated the ship before passengers was "going against tradition" and "common sense", a maritime expert told Daybreak.
Chris Ware also commented on reports the third officer was at the helm as the ship ran into trouble, saying an officer of that ranking should be "competent" enough to help evacuate passengers.
Local media is reporting that divers have entered the hull of the capsized South Korean ferry.
The third officer was at the helm of a South Korean ferry when it capsized, an investigating prosecutor told a news conference, Reuters reports.
The investigator added that the captain may not even have been on the bridge at the time.
"He may have been off the bridge ... and the person at the helm at the time was the third officer," the investigator said.
The death toll from a capsized South Korean passenger ferry has risen to 25.
Of 475 passengers and crew on the Sewol ferry, which capsized in calm seas on Wednesday, 179 people are listed as safe and 271 are still missing.
South Korean authorities were due to restart rescue efforts this morning, which will include the deployment of an unmanned submarine to inspect the vessel.
Divers - hampered by strong tides and murky waters - have so far been unable to gain access inside the ferry.
Rescuers are still trying to find hundreds of missing passengers who were onboard a capsized South Korean ferry.
China Correspondent Lucy Watson reports:
The death toll in the South Korean ferry disaster has now risen to 18, according to South Korean reports.