Search teams involved in the rescue of twelve schoolboys and their football coach trapped in a Thailand cave had little hope when they first started the mission.
On Monday, all 13 people were found alive after spending 10 days in the cave network.
Ben Reymenants, a diver on the search team, told Checkpoint with John Campbell the first days were really tough.
"The first day we decided it was never going to work, the outflow was so strong - it was really pulling hand over hand, the visibility was zero it was really mud flowing out.
"But then the rain stopped for a little while, the pumps were doing their job and we could actually see and then we progressed quite a bit," he said.
Listen to the interview with diver Ben Reymenants
When searching for the missing people he tried to stay focused and not think about the children.
"Sometimes you just have to turn around when all the red flags go up, and you're lost with your hands in the mud and you can't find another passage or you're stuck in a crevice and can't move," Mr Reymenants said.
"One time my buddy actually had to pull me out of a crevice by my fins because I couldn't turn around anymore."
It was a miracle the schoolboys and their coach were alive and mentally responsive, he said.
"Luckily, the coach in the end had some sense and stayed together in the dry and conserved their energy and that saved them," he said.
"Because [they spent] ten days no food, no light, just some water dripping from the walls and they're all together in a pile of mud."
Rescue teams say flooding has made the mission to free them difficult.
Options to get them out alive include teaching them to dive or waiting months for high waters to recede.
The real challenge now will be getting them out of the cave and keeping them alive while they wait.
"They can't swim, so imagine teaching them to dive in a short time frame - there's a real risk involved," Mr Reymenants said.
A number of Thai doctors volunteered to stay in the cave for the monsoon season to provide medical care if the children and the coach were not able to leave the cave for three to four months.