South Korean ship sinks

It was supposed to be a class trip to a resort island that's considered the Hawaii of Korea. Instead, the ferry has capsized in the Yellow Sea, and hundreds of people are unaccounted for.

The parents of students from a South Korean high school have been clutching their cell phones, waiting for a call from their children or rescuers.

On Tuesday night, 325 high school students from the city of Ansan departed on a ferry called Sewol for a four-day trip to Jeju Island. About 70% of those aboard were from the high school.

With 459 people on board, the Sewol pulled out of the port at Incheon at 9:30 p.m. Tuesday, according to JTBC, a CNN affiliate.

On Wednesday morning shortly before 9 a.m., one of the passengers, Kim Sung-Mook was eating breakfast in the ship's main hall when he felt the ferry tilt, he told CNN affiliate YTN.

At first, "we thought it was because of the tide," Kim said.

The waves had been smooth until the ship suddenly tilted, witnesses said.

The ship kept tilting further and an announcement blared through the loudspeakers warning passengers not to move as it would be dangerous.

Then, he heard a loud bang from inside the ship. Kim thought a crane on board had toppled over, he said.

When the sea water started gushing into the ferry, passengers began to scramble.

Elsewhere on the boat, one of the high school students Lim Hyung Min felt tremors throughout the ship that were strong enough to knock shipping containers off balance. Several of his classmates were flung off their feet as the boat began to lean into one side.

"The students were falling over and crashing into things and bleeding," Lim said.

The ship kept tilting further to about 90 degrees, passengers said.

Back in the main hall, Kim heard the buzzing of helicopters overhead. The cafeteria workers were dashing up to the deck.

"The helicopters arrived. They said they could take five more people, so we sent students," Kim said.

Footage from South Korean media showed helicopters hovering over a half-submerged ferry with panic-stricken passengers scrambling from the side of the boat.

Not everyone had made it to the top deck, because "the announcement asked not to move since it could be dangerous. So everyone stayed where they were. But when the water started coming in, people started moving to the upper level," he said.

Kim managed to get on a helicopter, but he saw as many as 30 people still trapped inside the ship. Shortly after his rescue, the ship capsized.

"Unless they broke a window, I think it would have been impossible for them to come out," Kim told YTN.

It remains unclear how many people have survived and how many are missing as the official numbers from authorities have been fluctuating throughout the day.

Inside the boat, Lim told YTN he stayed in the room until rescuers opened a door and threw life jackets at his direction. He was ordered to jump in the ocean, which he described as "unbearably cold."

After his rescue, Lim went on air on YTN to list the names of his classmates whom he had seen to reassure their parents that they were safe.

Meanwhile, parents had gathered at the Ansan Danwon High School, clutching their cell phones in an agonizing wait for a call from their children. Officials had posted a list of names in which each were being circled after confirmation of their rescue.

One woman who received a call was immediately swarmed by cameras as she received a call from her child. "Are you ok?" she cried out.

Although their own phones were lost in the water during the rescue, students have been borrowing rescuers' phones to call their parents. At one point, the school announced that all students had been rescued but soon rescinded the announcement, to the parents' wrath.

The students who fell into the water were "having difficulties due to their body temperatures dropping, but they have blankets and changed their clothes, so they're feeling better now," Lim told YTN.

The rescued students gathered in a gymnasium awaiting their parents and teachers. They have since departed the school in buses to reunite with their students, according to YTN.