The boys, aged 11 to 16, went exploring with their coach in the Tham Luang Nang Non cave system in Chiang Rai, northern Thailand, on June 23.
However, they became trapped for 10 days after sudden downpours flooded the narrow tunnels.
Despite being found by an international rescue team on Monday, they cannot be evacuated immediately.
The high water levels and narrow passages into the area where they are trapped means the group will have to learn how to dive to escape – which could take weeks or months.
In the meantime, the boys have reassured their parents they are safe and well by writing them notes about what food they would like to eat when they get out.
Here’s what some of them said in their letters:
Dom, 13 (Dwangphech Phromtheph) wrote: “I am fine, it is a bit cold but don’t worry. Please don’t forget my birthday.”
Nic, 15 (Phiphat Photi) said: “Mum and dad I love you, and I love nong [his brother or sister] too. If I can get out please take me to eat crispy pork. Love you mom, dad, nong.”
Thai cave rescue latest update: Parents have been waiting for their children to return for two weeks
Thai cave rescue latest update: A map shows the intricacies of the cave system
Bew, 14 (Aekarut Wongsukjan) added: “Please don’t worry, mum and dad. I have been gone for two weeks. I will go back and help you with the shop when I can. I will try to go soon.”
Tee, 16 (Phonchai Kumluang) wrote: “Mom, dad, brother and sister and family please don’t worry, I am very happy.”
Ekapol Chanthawong, the 25-year-old coach of the Wild Boars soccer team, also said sorry to the boys’ parents.
He wrote: “To the parents of all the kids, right now the kids are all fine, the crew are taking good care.
Thai cave rescue latest update: Divers are preparing to “buddy dive” with the team to free them
“I promise I will care for the kids as best as possible.
“I want to say thanks for all the support and I want to apologise to the parents.”
Experts initially thought the group could wait inside the cave for the monsoon season to finish in October.
However, low oxygen levels underground and torrential rain forecasts have started to speed up the rescue effort.
An experienced adult diver could now swim with each boy to evacuate them from the cave.