When a group of 13 school kids and their teachers boarded a boat on a school trip, they had no idea of the horror that was ahead of them.
Their boat capsized into freezing, icy water hundreds of metres away from the shore.
Somehow, some of them managed to swim back to land, but seven of the group didn't make it back and were left clinically dead in the water after being hit by extreme hypothermia.
But in what is believed to be the largest group of hypothermic victims to be successfully resuscitated, each of the teenagers somehow survived - suffering no brain damage - and their incredible story has amazed doctors.
Katrine was one of the group on the boat on that fateful day.
She told the BBC : "It was so freezing, it was so cold and there was ice on the water.
"I landed under the boat and when I came up from under the water the nightmare began.
"Everybody was screaming and everything was like unreal. You could just see the panic.
"The teacher said that we had to swim in because otherwise we would die.
Katrine managed to swim to the shore despite suffering extreme hypothermia but when she got to the land she found herself lost in a forest.
"It was really hard because you didn't have any strength in your legs. I kept falling down. In that moment, that was where I thought 'okay, now I'm going to die'.
"Then I saw the man. Thank God for that. When I saw him I was screaming so loud."
But her classmate Casper wasn't able to swim to the shore and his heart stopped while he was still in the water.
He said: "It was hard weather , it was very windy. The boat flipped in the middle of the sea then all the people fell out.
"I couldn't swim. One of my friends came over to me and tried to help me but after some time I was clinically dead because of the temperature of the water."
After two hours in the water they were finally rescued by paramedics.
Dr Steen Barnung was part of the air ambulance crew who arrived at the scene.
"This man comes running towards us and he repeats the same words. They're all dead. They're all dead. They're all dead.
As well as stopping their hearts, the hypothermia slowed their metabolism which meant their organs had a chance of restarting as they warmed up.
Dr Michael Jaeger Wansche, who was part of the team desperately fighting to save them, said: "They felt cold. They were ice cold. They're clinically dead young teenagers.
He said: "When you are as cold as they were, we know that we can resuscitate. They are dead but not really dead.
"We still have a chance."
When they arrived at the hospital doctors set to work warming the teenagers' blood at one degree every 10 minutes.
Six hours later, they heard a heart beat.
But their work was far from over and they then turned their attention to the teenagers' brains, as two million of its cells die every minute when deprived of oxygen.
The teens were all in comas so they had to wait a few days to learn the extent of the damage.
Recalling the moment Casper woke up, his girlfriend said: "I could see a hint of a smile and I knew he recognised me. I was so happy. I can't describe the feeling.
"Everyone was so happy because everybody awoke that day.
"Every parent was in the waiting room and we just got out of there and screamed and jumped."
There were no abnormalities on their scans, making the group the largest group of hypothermic victims that have been successfully resuscitated.
The teenager's lives have changed forever since the accident.
Katrine said: "When you have nearly died, it's just a little different. Mentally, sometimes I get some breakdowns.
"The worst part if maybe when I'm in school because I'm not that good with remembering things. I have learnt what's important and what's not important. What is worth fighting for.
"I'm really happy that I'm alive."
