The mobile-phone footage also shows the high school students huddled below deck wondering if they would make the news and discussed posting about the drama on Facebook.
But later one leaves "farewell words" and another sends a message of love to their mother.
The shaky video was on the phone of 17-year-old Park Su-hyeon when rescuers recovered his body. The boy's father, Park Jong-dae, has released it to the Associated Press and South Korean media, saying he wanted to show the world the ship's condition as it sank.
It shows the fear in the cabin as the listing becomes worse.
Some say they feel dizzy, that their legs are shaking. One student can be seen walking with his hands against the wall for balance.
"Am I really going to die?" a student in the video asks at 8.53am on April 16, less than two minutes into it and the same time a crew member on the bridge made the first distress call.
Students are heard asking whether the ship will sink and where their teachers are.
Several times they are warned over the loudspeaker to stay where they are, even as the tilting increases and it becomes less possible for them to flee.
The tragedy, which has left more than 300 people dead or missing, has created a sense of national mourning, anger and shame.
Nearly 220 bodies, mostly from inside the submerged vessel, have so far been recovered.
More than 80% of the victims were students from one high school in Ansan, south of Seoul, on their way to the tourist island of Jeju for a school trip.
The group of teens in the video alternate between bluster, attempts at humor and unmistakable fear.
Captain Lee Joon-seok and 14 others responsible for the ferry's navigation have been detained on suspicion of negligence and abandoning people in need.