As they started to leave, they found their exit path flooded. "At least we were trying to do something", he said.
They thought up a plan to dig a passageway for the water to flow through - but it didn't go down at all.
King Maha Vajiralongkorn has granted permission for a party in the Royal Plaza, a public square in Bangkok's old town, to thank the Thai and foreign participants in the rescue, the government said.
His coach, 25-year-old Ekkapol Ake Chanthawong, told the group to stay quiet.
"Yes, we all can swim", the coach said. Their bikes and other items were found outside the Tham Luang cave complex, triggering a massive search that ended nine days later when rescue teams found the boys on a high ledge, trapped after the cave began filling with floodwaters.
In order not to think about food, they drank water to make themselves feel full. "The vans are leaving", said a Reuters witness, as the boys, wearing T-shirts emblazoned with a red graphic of a wild boar and backpacks slung over their shoulders, went past a crowd of cameras to enter the vans.
The dramatic mission to save the group captured the world's attention, with heads of state, celebrities and even soccer stars at the World Cup in Russian Federation sending good wishes and messages of hope to the boys and the team of divers and rescue experts. "I tried not to think about fried chicken or some chili dip".
"I suggested that we dig a small channel, so that we could drain the water out of the way". Many of them could swim - contrary to initial reports - and so they tried to venture out.
"We'll do whatever he wants", he said. Now the paperwork has been submitted to officially recognize them as Thai citizens. Many said they want to be either professional footballers or Thai Navy SEALs.
This contrasted to an average of 4kg lost during the more than two weeks they were trapped.
The voices of the two British divers who called out to them, Rick Stanton and John Volanthen, were a "light of hope", the boys said.
Thai cave boys leave hospital and give first TV interview since being rescued
"Suddenly, we heard somebody talking", the teen said. "We have to eat, eat, eat". Rising waters and plummeting oxygen levels convinced rescue workers that something needed to be done sooner rather than later, despite the fact that expert divers said the cave posed some of the toughest conditions they'd ever faced.
They went inside, leaving their bicycles, backpacks and soccer shoes near the cave's entrance.
The 12 members of the Wild Boars soccer team and their coach subsisted on water that flooded the cave where they were trapped for two weeks - and they now regard the divers who saved them as family, they said at a news conference on Wednesday after finally leaving a hospital and preparing to return to their homes in northern Thailand. A psychologist pre-screened the questions before the hour-long conference.
"We don't know what wounds the kids are carrying in their hearts", said Tawatchai Thaikaew, an official at the Thai justice ministry.
The Wild Boars team entered the news conference to applause from reporters and classmates and put on a quick demonstration of their skills on a miniature football field set up in the hall where they met the media in Chiang Rai.
"Everybody was happy, it was the most hopeful moment in 10 days".
Upon hearing about the death of a volunteer rescue diver and former Thai navy SEAL taking part in the mission, everyone was in shock, they said.
The public relations department in Chiang Rai province solicited questions from news outlets in advance and they will be forwarded to psychiatrists for screening.
All members of the team confirmed at the conference that they will become monks to honour Kunan's memory.
Titan, the team's youngest member, said, "I had no strength".More news: France's World Cup team given heroes' welcome in Paris