With water quickly flooding the decks and a mammoth South Korean ferry about to sink, desperate students took to their smartphones Wednesday to text their last goodbyes.

“Mom, I want to say this before it’s too late,” one student wrote. “I love you.”

That student is among the 290 reported still missing.

Another student traded texts with his mom, who had no clue the ferry was in danger.

“Mom, I might not be able to tell you in person. I love you,” the student texted, according to a Korean news agency.

“Me too, son. I love you,” the mother texted back, followed by three heart symbols.

He was among those rescued from the boat, the Sewol.

“Dad, don’t worry. I’ve got a life vest on and we’re huddled together,” a high-school girl wrote.

“I know the rescue is under way, but make your way out if you can,” he replied.

“Dad, I can’t walk out,” she replied. “The corridor is full of kids, and it’s too tilted.”

She is still missing.

The waters were calm off South Korea’s southern coast where the ferry carrying high school students on an overnight trip to a tourist island went down just after breakfast.

But on board, there was confusion and chaos, with some passengers being told to plunge into the cold, murky water, and others instructed to stay on board.

“We were told to stay where you are, so we kept staying,” a survivor told YTN. “But later on, the water level came up. So we were beside ourselves. Kids were screaming out of terror, shouting for help.”

Student Lim Hyung-min told reporters that he jumped into the ocean wearing a life jacket with other students and then swam to a rescue boat.

“As the ferry was shaking and tilting, we all tripped and bumped into each another,” said Lim, who jumped in the ocean. “The water was so cold and I wanted to live.”

Lee Gyeong-og, a vice minister for South Korea’s Public Administration and Security Ministry, said 30 crew members, 325 high school students, 15 teachers and 89 nonstudent passengers were aboard the ship.

More than 50 people were reported injured.

Experts said the vessel may have veered off course in dense fog, and most likely struck something in the water.

“So if they hit something, that would have meant they were out of the channel, which is quite easy to do,” Mary Schiavo, former US Department of Transportation inspector general, told CNN.

“What people don’t see when they look at the glassy expanse is underneath, there are intricate and detailed channels maintained. If it got out of the channel, it could have hit something.”

The ferry took only two hours to sink.

“There was a bang and then the ship suddenly tilted over,” said a 57-year-old survivor, identified only by his surname, Yoo.

“Downstairs were restaurants, shops and entertainment rooms, and those who were there are feared to have failed to escape,” he said.

Divers operating in 50-degree water at a depth of at least 90 feet entered the vessel but found no survivors or bodies, according to navy officials.

Jeong Kyung-mi, mother of another 17-year-old from the school, was more fortunate. She received a text message from her son saying he had been rescued with friends and was safe.

“When I heard the news, it felt like my heart had stopped beating.”

Dozens of boats, helicopters and divers were on hand to rescue passengers. About 95 percent of the ship was submerged when the operation began.

Television footage showed rescuers pulling passengers in life vests out of the water as their boats bobbed beside the ferry’s hull. Other passengers were winched to safety by helicopters.

Survivors were taken to nearby Jindo Island.

A massive rescue effort resumed after a delay of several hours. Cold water, swift currents and low visibility were complicating the operation.