More rain is forecast over the weekend, mounting pressure on rescuers to come up with a plan to rescue the team before the water level rises even higher.
ThaiNavy SEALssaid they are confidence they might be able to free the boys "as early as this morning".
The boys, aged 11-16, and their 25-year-old coach disappeared after they went exploring in the Tham Luang Nang Non cave in northern Chiang Rai province after a soccer game June 23.
They were found on Monday night by rescue divers, on a rock shelf about 4km (2.5 miles) from the cave mouth.
They have been joined by Royal Thai Navy SEALs and are also supplied with soft food, water, light, medicine, thermal blankets and diving gear. Instead, crews will focus on pumping out water from flooded passageways leading to the Nern Nom Sao slope where the boys and their coach were found inside. Several of the boys are seen smiling as they interact with the navy SEAL, who cracks jokes.
Thai authorities said they are working to install an Internet cable to the cave so that the parents of the boys can talk to their children.
Tham Luang operation commander, Narongsak Osotthanakorn, said unregistered volunteers had been diverting water back into the ground in the belief that they were helping.
"It's like he has been given a new life", she said, adding that she will never let her son go into a cave or near water again.
That's the predicament a youth soccer in Thailand team is in.
Many, if not all, of the boys reportedly do not know how to swim.
"This requires them do be psychologically able to cope with being underwater. and the dives being not too long or hard", Alan Warild, an expert from the NSW Cave Rescue Squad in Australia, said.
Chiang Rai provincial Gov. Narongsak Osatanakorn said Wednesday that the team may not all be extracted at the same time depending on their health.
"Thai Interior Minister Anupong Paojinda has said the boys" only chance is to swim out through the flooded underground network and that swimming lessons will start on Wednesday or Thursday. That's obviously risky. Yookongkaew said authorities "have to be certain that it will work and have to have a drill" to make sure "it's 100 percent safe", the AP reported.
A medic who's evaluated their conditions said Thursday the boys and their coach are malnourished and exhausted - not well enough for an immediate extraction.
The 12 young boys and their football coach were discovered rake thin and hungry on a mound of mud surrounded by water late on Monday, ending an agonising search that captivated a nation.
There is no simple solution for the 12 boys and their football coach, who are being looked after by Thai military divers and an global team of underground rescue experts.
Other rescue options are still being considered, one of which involves looking through the mountains and seeing if there's an air hole they can dig through to get the team out that way.
Rafael, 53, who is from Israel but has lived in Thailand for more than 30 years, said he had been inside the cave 25 years ago and found that it was more hard to navigate than other caves he had tackled.
Monsoon rains are forecast to pummel the region Sunday as Thailand enters its wet season.
The boys remain weak after spending days in the darkness, barely moving from the small, muddy ledge, away from the water.
A cave diving instructor with 15 years of experience, who only wished to be known as Chew, said that his students are typically trained in open waters with blacked out diving masks to simulate poor visibility.
"I'd speculate it could be helpful - even if it functioned exclusively as a way for the children to feel like their coach was doing something to help them", said Michael Poulin, a professor of psychology at the State University of NY at Buffalo.
It was unclear what the options were to get the "Wild Boar" team out of the Tham Luang caves in Chiang Rai Province and how they would be steered through tight, fluid conditions and uncertain weather.