Mae Sai, Thailand (CNN) For the Buddhist monks who keep nightly vigil outside the cave where 12 young boys and their soccer coach remain trapped, the dry weather is a sign their prayers are working.

The Thai authorities know it too.

Monsoon season typically lasts from July to October. During that time, water levels in Mae Sai, which sits nestled along Thailand's mountainous border with Myanmar, can rise rapidly, flooding farmland and cutting off entire villages.

The Tham Luang Nang Non caves, where the boys are trapped, act as the town's natural drainage basin during this period of heavy rains.

The boys and their 25-year-old coach are huddled together in a small chamber four kilometers (2.5 miles) inside of the cave network, with a limited supply of oxygen.

To reach them, expert divers must carefully traverse jagged passageways, occasionally narrowing to the width of a person, forcing divers to remove their breathing tanks from their backs and enter like a pencil, taking extra care not to snag their wetsuit. The tunnels are pitch black. The water is muddy and cold. The whole journey can take up to six hours.

All relatives can do is wait as hundreds of rescuers work on multiple plans to get the boys out.

For almost two weeks, authorities have been pumping water from the caves, 24 hours a day. Such is the volume of water extracted that entire nearby fields have been transformed into lakes.

The banks along the road leading to the cave's entrance are now a freshwater stream, used by exhausted rescue workers each morning to bathe.

Earlier in the week, efforts to lower the water levels had generated an air of optimism. During a press conference Thursday, one Thai official suggested that the kids may even be able to "walk out."

Hundreds of rescuers with equipment continue the rescue operation at the Tham Luang Nang Non cave on July 6.

Such hopes have now vanished, replaced instead with a mounting sense of urgency. People at the large makeshift camp that now surrounds the caves liken the mood to that of a hostage situation.

Dark clouds drift ominously overhead. Weather forecasters predict heavy rains throughout the coming week.

The chamber in which the boys are located is no longer thought safe. Even if they are given enough food to wait out the rainy season, there is no guarantee that the ledge they are sitting on will not be submerged.

There are no easy decisions. But with the flood waters expected to rise in the coming days, a decision will have to be made soon.

"The teams there will have a tipping point where they have to make that call to bring them out. To leave them there would almost certainly result in them drowning," said one British mining engineer and experienced cave diver, who did not wish to be named due to the sensitivity of the subject.

"The tipping point will be related to how much rain is starting to fall, water levels inside, versus how the boys are doing. They'll be looking at flow rates, recorded rain fall over the past weeks, months to get a rough indicator of where they're at, they'll have a deadline in mind, and then they'll go for the most unpopular way out," he added.

Each day rescuers at the camp talk of differing strategies. Drilling holes, expanding the tunnels, pumping out water.

Earlier this week, authorities announced that the boys, the youngest of whom is just 11 years old, would undergo a crash course in scuba training in the hopes that they might be able to dive out.

JUST WATCHED Watch rescuers reach soccer team stuck in cave Replay More Videos ... MUST WATCH Watch rescuers reach soccer team stuck in cave 01:38

Though fraught with risk, friends and family had warmed to the idea, encouraged by news that diving teams from around the world had arrived on site to lend their expertise.

On Thursday, classmates of the boys at Prasitsart School had talked excitedly about their friends swimming bravely to safety with the help of foreign divers.

It would be "no problem" they assured us, their friends were more than capable, and besides they have the best divers in the world helping them.

On Friday, that option appeared to fade with news that a former Thai Navy SEAL, volunteering in the rescue effort, had died while swimming through the cave passageways.

Former Sgt. Saman Kunan died on Friday due to a lack of air while attempting to return to a command center deep underground.

No one in Mae Sai is prepared to think the worst, let alone say it aloud. But the mood among the community is beginning to shift, as the reality of the situation takes hold.

At a school attended by one of the missing children a teacher asked how the boys could possibly complete a journey that was too tough even for a former Thai Navy SEAL?

News that some of the boys, especially the younger ones, are suffering from malnutrition, has added to those fears.

In the town's main market, where TVs remain permanently tuned to the news, people chatted nervously of the need to find other options. Surely, they can drill an opening in the roof of the cave, they asked.

A WhatsApp group chat popular with some of the older school kids in the town said that a famous American engineer called Elon Musk was sending help. Maybe that would prove the difference.

But it is the families of the children who feel these questions most keenly.

At the Anubanmaesai primary school, where the youngest of the 12 missing boys, 11-year-old Chanin Viboonrungruang, is in his final year, the school's principal talked of his concern for the boy's parents.

"I'm afraid that the parents will begin to think the same thing will happen to their son," said Radap Tate, of the Navy SEAL's death on Friday.

Chanin Viboonrungruang, 11, is in his final year of Anubanmaesai primary school in Mae Sai.

Tate regularly visits Chanin's parents at the site of the cave where they keep a constant vigil. They need good news he tells us. "Rescuers need to find an opening to the roof of the cave."

The idea of an opening in the roof of the chamber is considered by many the "miracle solution," a way out that would immediately solve the issue of low oxygen levels and allow the boys to leave without having to navigate moving flood waters.

On Saturday morning, Kamolchai Kotcha, director of the National Parks Authority, told journalists that the process of looking for openings and holes at the top of the mountain above the caves was still ongoing.

"What we have done so far is not nearly enough, in my personal opinion. So, we must continue more diligently," said Kotcha.

"Tonight, more than likely we will be spending the night up there in the forest. At the same time, we are still moving equipment as well as maintaining traffic control in the area."

To date, Thai authorities have drilled more than 100 holes in the mountain. They've earmarked 18 as having "potential," though while some run as deep as 400 meters, non are thought to lead directly to the boys' cavern.

Thousands of volunteers, members of the Thai military, and international rescue experts are participating in the search effort. The will to succeed is strong and people here will not give up.

But pressure is building.

In a joint letter from the missing children posted to the Facebook page of the Thai Navy SEALs on Saturday, the boys attempted to reassure their parents that they are OK and will be out soon.

"I love everybody. I'm happy in here," writes one of the trapped boys , in neat blue pen. "The seals take really good care of me. I love everybody."

For the Buddhist monks and the hundreds of others keeping vigil at the site, the message is a shared one, as they enter into Saturday evening, with the hope that by Sunday, their boys will be free.