South Korean ferry “Sewol” is seen sinking in the sea off Jindo April 16, 2014, in this picture provided by Korea Coast Guard and released by Yonhap. Almost 300 people were missing after a ferry sank off South Korea on Wednesday, the coastguard said, in what could be the country's biggest peacetime disaster in nearly 20 years. (Photo by Reuters/Yonhap/Korea Coast Guard)

People watch a TV news program showing a sinking passenger ship, at Seoul Railway Station in Seoul, South Korea, Wednesday, April 16, 2014. The South Korean passenger ship carrying more than 470 people, including many high school students, is sinking off the country's southern coast Wednesday after sending a distress call, officials said. There are no immediate reports of causalities. (Photo by Ahn Young-joon/AFP Photo)

Coast Guard officers conducting a rescue operation around the passenger ferry Sewol sinking in waters off the southwestern coast of South Korea. (Photo by EPA/Yonhap)

Part of South Korean passenger ship “Sewol” that has been sinking is seen as South Korean maritime policemen search for passengers in the sea off Jindo April 16, 2014. (Photo by Hyung Min-woo/Reuters/Yonhap)

Parents search for their children's names among a list of survivors rescued from a ferry that sank off the country's southern coast, at Danwon high school in Ansan, South Korea, April 16, 2014. (Photo by Ahn Young-joon/AP Photo)

Passengers from the ferry sinking off South Korea's southern coast are rescued by the South Korean Coast guard in the water off the southern coast near Jindo, south of Seoul. (Photo by AP Photo)

South Korea coast guard police officers work to rescue passengers from a South Korean passenger ship, at Mokpo Coast Guard in Mokpo, south of Seoul, South Korea, Wednesday, April 16, 2014. (Photo by Cho Keun-young/AP Photo/Yonhap)

South Korean ferry “Sewol” is seen sinking in the sea off Jindo April 16, 2014, in this picture provided by Korea Coast Guard and released by Yonhap. (Photo by /Reuters/Yonhap/Korea Coast Guard)

In this image taken from video released by News Y via Yonhap, passengers from a ferry sinking off South Korea's southern coast, are rescued by a South Korean Coast Guard helicopter in the water off the southern coast near Jindo, south of Seoul, Wednesday, April 16, 2014. (Photo by AP Photo/Yonhap)

Part of South Korean passenger ship “Sewol” that has been sinking is seen as South Korean maritime policemen search for passengers in the sea off Jindo April 16, 2014. (Photo by Hyung Min-woo/Reuters/Yonhap)

An injured passenger is given medical care after being rescued by South Korean crews. (Photo by News1/Reuters)

A mother weeps as she and others search for their children's names among a list of survivors rescued from a ferry that sank off the country's southern coast, at Danwon high school in Ansan, South Korea, Wednesday, April 16, 2014. (Photo by Ahn Young-joon/AP Photo)

South Korean ferry “Sewol” is seen sinking in the sea off Jindo April 16, 2014, in this picture provided by Korea Coast Guard and released by Yonhap. (Photo by /Reuters/Yonhap/Korea Coast Guard)

A rescued passenger from a ferry sinking off South Korea's southern coast, is carried by police and rescue teams on his arrival at Jindo port in Jindo, south of Seoul, South Korea, Wednesday, April 16, 2014. (Photo by Park Chul-heung/Reuters/Yonhap)

Part of South Korean passenger ship “Sewol” that has been sinking is seen as South Korean maritime policemen search for passengers in the sea off Jindo April 16, 2014. (Photo by Hyung Min-woo/Reuters/Yonhap)

Rescued passengers are escorted by members of a rescue team upon their arrival at a port in Jindo, south of Seoul, South Korea, Wednesday, April 16, 2014. (Photo by Park Chul-heung/Reuters/Yonhap)

In this photo released by Jeollanamdo via Yonhap News Agency, South Korean rescue team boats and fishing boats try to rescue passengers of a ferry sinking off South Korea's southern coast, in the water off the southern coast near Jindo, south of Seoul, Wednesday, April 16, 2014. (Photo by AP Photo/Jeollanamdo via Yonhap)

A girl rescued by South Korean maritime policemen from a sinking ship “Sewol” in the sea off Jindo, is treated at a port in Jindo April 16, 2014. (Photo by Hyung Min-woo/Reuters/Yonhap)

South Korean coast guard officers watch on as the ferry Sewol sinks in the water off of the country's southern coast, April 16, 2014. (Photo by Hyung Min-woo/AP Photo/Yonhap)

Rescued passengers from a ferry sinking off South Korea's southern coast, are escorted by rescue teams on their arrival at a port in Jindo, south of Seoul, South Korea, Wednesday, April 16, 2014. (Photo by Park Chul-heung/Reuters/Yonhap)

The mother of a passenger who was on a sinking ferry reacts as she finds her son at a gym where rescued passengers gather in Jindo April 16, 2014. (Photo by Kim Hong-Ji/Reuters)

A rescued passenger from a ferry sinking off South Korea's southern coast, is carried by rescue teams on his arrival at Jindo port in Jindo, south of Seoul, South Korea, Wednesday, April 16, 2014. (Photo by Park Chul-heung/Reuters/Yonhap)

Parents wait at Danwon High School in Ansan, South Korea, after the ferry their children were riding in sank, April 16, 2014. (Photo by Ahn Young-joon/AP Photo)

South Korean coast guard officers try to rescue passengers from a ferry sinking in the water off the southern coast near Jindo, south of Seoul, South Korea, Wednesday, April 16, 2014. The ferry carrying 459 people, mostly high school students on an overnight trip to a tourist island, sank off South Korea's southern coast on Wednesday, leaving nearly 300 people missing despite a frantic, hours-long rescue by dozens of ships and helicopters. At least four people were confirmed dead and 55 injured. (Photo by AP Photo/Yonhap)

A relative waits for their missing loved one at a port in Jindo, South Korea, Wednesday, April 16, 2014. A ferry carrying 459 people, mostly high school students on an overnight trip to a tourist island, sank off South Korea's southern coast on Wednesday, leaving nearly 300 people missing despite a frantic, hours-long rescue by dozens of ships and helicopters. (Photo by Ahn Young-joon/AP Photo)

South Korean ferry “Sewol” is seen sinking at the sea off Jindo April 16, 2014. (Photo by Kim Hong-Ji/Reuters)

South Korean ferry “Sewol” (L) is seen sinking at the sea off Jindo, as lighting flares are released for a night search, April 16, 2014. (Photo by Kim Hong-Ji/Reuters)

South Korean relatives of passengers on board a capsized ferry cry as they wait for news about their loved ones, at a gym in Jindo on April 17, 2014. The frantic search for nearly 300 people, most of them schoolchildren, missing after a South Korean ferry capsized extended into a second day on April 17, as distraught relatives maintained an agonising vigil on shore. (Photo by Jung Yeon-Je/AFP Photo)