JINDO, South Korea, April 16 (Xinhua) -- The mother of a high school student could not hold back her tears of relief when she found her son's name on the survivors list, while parents of those who remained missing started wailing and soothed each other in tearful hugs.
Authorities have gathered relatives of passengers on a sunken ferry carrying some 470 passengers and crew -- mostly high school students bound for the southern resort island of Jeju, at a gym on nearby Jindo island.
Yet some parents were so anxious they could not stay indoors. They rushed to Jindo harbor, wrapped in blankets, hoping for news of their children in the wind and cold.
At least four people have been confirmed dead and 174 rescued, while almost 300 remain missing after the vessel, the "Sewol", listed to one side and sunk within two hours Wednesday morning. It could be South Korea's biggest sea disaster in more than 20 years.
The students were from the Danwon High School in Ansan, a Seoul suburb. Most of them were in their first or second year. They were sailing from the port of Incheon to Jeju on a four-day spring trip.
"I heard a big thumping sound and the boat started to tilt," one survivor said.
"I ran out to have a look and saw the ferry listing by 90 degrees," said Mr. Yoo, who is 57 years old.
He said the ferry had three decks, with a canteen, shops and entertainment facilities below.
"Since water poured in suddenly and submerged all the floors quickly, many people staying in lower cabins were trapped and had no time to escape," Yoo recalled.
Several survivors said they had been ordered to stay in their seats and not to move. When the vessel tipped sharply, the passengers bumped into each other and some of them were injured by falling luggage and goods containers.
Mr. Kang, another survivor, said events happened within a very short period of time. He narrowly escaped but there was no time for him to help others.
Some passengers put on life jackets and jumped into the sea. They clambered into inflatable boats and were rescued by Coast Guard vessels and fishing boats.
The ship sent out a distress signal at about 8:52 a.m. Wednesday and had remained afloat on its side for about two and a half hours before finally sinking.
After receiving the SOS, South Korean authorities, including police, fire, Coast Guard and Navy, dispatched 72 ships and 18 helicopters to the scene.
About 5 p.m. local time, a team of South Korean Navy divers succeeded in entering the sunken vessel and searched three of its compartments, but found no bodies.
The ship sank at a depth of 30 meters, with the ocean currents flowing at a speed of 8 km per hour. Waves were half a meter high. Water temperature was 11.7 Celsius degrees, under which conditions a human body can endure only one or two hours.
South Korean President Park Geun-hye was immediately briefed on the accident, and she ordered maximum efforts be made to rescue all passengers, stressing that all available Navy, Coast Guard and other vessels nearby should be mobilized.
"There is not much time left before sunset. Please make the best efforts to rescue even one more person," President Park said during a visit to the central disaster management office in Seoul. Park said she felt "truly devastated."
Officials from South Korea's Security and Public Administration Ministry said the cause could be confirmed only after rescue and search work concluded.
However, South Korean media quoted some of the rescued passengers as saying a loud sound was heard before the ship started to list and then sank at around 11:30 a.m. local time. The ship was believed to have hit a submerged rock or another ship in foggy conditions.
South Korea's YTN reported the "Sewol" captain was acting in the role and it was unclear whether he was familiar with the voyage route. YTN also reported the ship's departure time from South Korea's western port city of Incheon on Tuesday night was delayed. There was a possibility the ship changed its route in order to make up time.
The ship was not equipped with a voyage data recorder because it was a coastal ferry that sails relatively short distances, the Korea Times reported.
The 6,825-ton ship was built in Japan in 1994 and, after 18 years of operation, was acquired by South Korea in 2012 and began plying the waters in March last year.
Two Philippine passengers aboard were rescued and sent to hospital for treatment.