It's a race against time as Thai rescuers struggle to rescue the 12 boys and their soccer coach from the flooded cave with a heavy rains expected over the weekend.
Rescue teams in the meantime began imparting crash courses in swimming and diving to the young soccer team to help them undertake the complex underwater journey.
"Now we are teaching the children to swim and dive," Deputy Prime Minister Prawit Wongsuwan told reporters. He added, "The water is very strong and space is narrow. Extracting the children takes a lot of people."
On Thursday, the Thai Navy SEALS posted photographs of members working in chest-deep water in the cave, trying to pump out water "fast as possible".
Divers, medics, counsellors and Thai navy SEALS were with the 12 schoolboys and a 25-year-old assistant coach, providing medicines and food while experts assessed conditions for getting them out safely, a task the government said would not be easy.
About 120 million litres of water had been pumped out by late on Tuesday, or about 1.6 million every hour. Rescuers are now trying to figure out how to get the children out, through several kilometres of dangerously flooded tunnels, or even to attempt to bring them out for now.
One of the options is that the 13 stay put in the Tham Luang cave until the flood waters recede, at the end of the rainy season in about four months.
But some officials say the boys could be out in days if the weather is on their side and enough water can be pumped out of the cave network to enable the boys to get out the same way they got in, just before heavy downpours hit the region, on foot through muddy tunnels, perhaps with some swimming.
A third option would be to teach the boys to use scuba gear, and they then dive through the flooded tunnels, the way their rescuers reached them. A fourth possibility would be to find an alternative way into their chamber.
A video released by the SEALS showed two rescuers seated on an elevated part of the cave beside boys wrapped in emergency foil blankets who appeared to be in good spirits, occasionally laughing.
A torch is shone on each boy, who says hello and introduces himself with head bowed and palms pressed together in a traditional "wai" greeting. One wears what appears to be the red jersey of the England soccer team in Tuesday`s World Cup second-round victory over Colombia. Another wears the blue shirt of English team Chelsea.
With Reuters inputs