The boys had to travel about 2.5 miles (4 kilometres) with oxygen tanks, tethered to cave divers to exit. About 0.6 miles (1 kilometre) of the journey was underwater, where everyone had to wear full face masks.
Over the past few days, the boys were given lessons in swimming and diving before they started their journey out of the cave.
Experienced cave divers have noted how difficult the dive in Thang Luam Cave is. In addition to having no experience diving, the boys have mostly been without food and medicine for two weeks in tight quarters where oxygen is limited.
On Friday, officials warned that oxygen levels in the cave dropped from 21 percent to 15 percent, further complicating rescue efforts. A Thai Navy SEAL commander told reporters he believed there was "a limited amount of time" left to rescue the soccer team.
How they got out
For the first four rescues, two divers accompanied each boy, one from the side and one from behind. They made their way back to the entrance of the cave guided by a 3 mile (4.8 kilometre) rope.
In total, 13 foreign cave divers and five Thai Navy SEAL divers participated in Sunday's rescue, according to Reuters.
The boys had to navigate through flooded passages that are no more than two feet wide in some areas.
According to the Thai government, when they reached a spot that couldn't fit a person and an oxygen tank, the divers would take the boy's tank off his back while slowly guiding the boy through the narrow passages.
The first boys exited the cave several hours before they were expected to – each leg of the journey was estimated to take six hours. Narongsak Osottanakorn, the Chiang Rai governor and head of the rescue mission, said that "today, everything was smooth".
The rest of the rescues were put on hold Sunday night while air tanks and other systems are refilled.
Racing against the rain
The boys were trapped in the cave when unexpected rains made their trip out impossible. For the last several days, crews have been trying to drain enough water out of the cave to make the rescue easier.
Officials recognise that they have to finish the recuses quickly, before seasonal monsoon rains arrive and flood the caves even further.
Osottanakorn told reporters that the team had rehearsed the plan for several days, and had cleared a sizeable amount of the flooding from the cave.
The rescue has captured the world's attention, and many have offered their ideas on how to get the team out.
Tesla CEO Elon Musk suggested creating a tunnel out of tubes in order to avoid diving.
He also floated using a small submarine that's "Light enough to be carried by 2 divers, small enough to get through narrow gaps."
Rescuers didn't use Musk's ideas to get the first four boys out, but Musk tweeted that he's communicating with the Thai government and other experts on the submarine idea.
On Sunday, Musk posted photos and video of the "kid-size submarine" his team was testing in LA. He said they would send it to Thailand Sunday evening.
This article was originally published by Business Insider.
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