This week marks the fourth anniversary of the dramatic rescue of 12 members of a soccer team and their coach from the Tham Luang cave in Thailand when the cave system flooded during an early start to the monsoon season.
The group was trapped for 18 days between June 23 and July 10, 2018, and was eventually rescued by a group of experienced divers that were able to free them with only minor injuries.
But that dramatic rescue that had the eyes of the world watching took a lot of planning to make sure everyone made it out.
"I remember the rain," said Australian anesthesiologist and cave diver Dr. Richard Harris. "This monsoon rain event happened early in Thailand and trapped these boys in the cave. So, rain and mud is my first and strongest memory."
Harris was one of the heroic cave divers who eventually helped lead the boys out of the cave to safety and said the early start to the monsoon season was why the boys became trapped.
"It was the rain that caught the kids in the cave in the first place," he said. "That really defined the whole event. If it wasn't for the early monsoon, the children would have been able to walk straight out again the same way they got in. But the impending continuing rain was the factor in determining a very short timeline that we had to rescue the children."
Harris spoke with FOX Weather from his home in Australia and said by the time he arrived at the site, he was told there was little time left to rescue the group.
"We had three to five days before the monsoons would return, and once they did, we would have no opportunity to dive back into the cave again," he said. "This river that was flowing out of the cave would overwhelm any kind of diving operations, and the kids would be stuck and would perish inside the cave. So we had to act really fast."
Initially, when the group entered the cave, there was no inclement weather around, and a sign outside of the cave warned people that the period from July to November was the cave flooding season.
Given they entered the cave in June, they presumed they would be able to explore and make it back out.
"What they didn't realize was that it had started raining over the back of the next mountain range, and the cave was already starting to soak with water," Harris said. "And at the far end of the cave, they turned around to come back out. They'd just been walking through a dry cave, and then suddenly they realized that the tunnel in front of them was blocked by water."
According to the United Kingdom's Met Office, the monsoon season runs from July and October, and the rain in the first few months is usually the heaviest but inconsistent.
With more heavy rain approaching the area, plans were developed to get rescuers inside the cave to make their way to the group, which was about 2.5 miles from the entrance.
Then, someone came up with a brilliant idea - providing anesthesia to the boys, so rescuers could pull them all out safely.
"The fear was that if we tried to take (the boys) through the cave, through this flooded cave with diving equipment, that they would panic and drown themselves and perhaps also the divers," Harris said. "So, I was asked to go there as an anesthesiologist and a cave diver and use that combination of skills to attempt this rescue."
One by one, the members of the soccer team and their coach were taken out of the cave and brought to safety.
Since the dramatic rescue, Harris said he has been back to Thailand a few times and met with some rescued boys.
"It's very emotional, as you can imagine because really we had no expectation that any of the boys would come out alive," he said. "So, you know, we were so pleasantly surprised, of course, when every single one of them survived the very difficult exit out of the cave and to see them back with their families."