The 12 boys trapped in a cave in northern Thailand are being trained in how to breathe with scuba equipment as they prepare for a possible attempt at leaving the cave.

Thai authorities are racing to drain water from the cave where the boys and their football coach are stranded before storms arrive, after which extraction will become “almost impossible” for months, according to a coordinator of the international rescue effort.

Plans to rescue trapped Thai boys rapidly developing Read more

Teaching the boys, none of whom knows how to swim, to use breathing apparatus so they can be escorted out of the cave system by rescue divers, is thought to be the most realistic option that would allow boys to be rescued from the caves before monsoon rains hit later in the week.

While they are learning to use the gear, none has made any attempt to get through the water hemming them in. Even if authorities manage to drain enough water to allow the boys to crawl most of the way out of the cave, they would still need to pass through short underwater passages.

Thailand cave rescue: fresh video emerges of football team in good spirits – live Read more

Ruengrit Changkwanyuen, a coordinator of the Thai contingent of the international cave diving team that located the boys on Monday night, said the group was on high ground and safe from flash flooding.

“But rescuers have to work quickly because by Friday a storm is coming, and if the rain starts again the cave is going to be fully flooded,” Changkwanyuen said. “If that happens it will be almost impossible to send supplies or keep in touch with them.”

New footage emerged of the children on Wednesday morning showing them being treated by a Thai navy doctor who spent the night around four kilometres inside the cave complex where the boys have been trapped for the past 11 days.

A nurse and up to four soldiers are also with the group in a raised cavern near an area known as Pattaya Beach and were monitoring their health and trying to keep their spirits high. “We are taking care of them as our own kids,” said Narongsak Osatanakorn, the governor of Chiang Rai province.

A spokesman for the Thai government said the mental health of the boys had been managed by their coach throughout the ordeal. “[He] is advising them that they need to lie down, of course meditation, try not to move their bodies too much, try not to waste their energy,” lieutenant-general Werachon Sukondhapatipak said.

Authorities said they appeared mentally and physically healthy after receiving food and water supplies, but were yet to speak to their parents. An attempt to send a mobile phone into the cavern was botched when a waterproof seal around the device was broken. They are preparing to send another.

Facebook Twitter Pinterest A team of Royal Thai Navy SEAL divers inspecting the water-filled tunnel in the Tham Luang cave. Photograph: AFP/Getty Images

“Once the phone gets to them, we want the families to talk with them and a lot of pressure will be relieved,” an army spokesman said on Tuesday.

Thai officials said on Tuesday that no extraction was imminent. “Today we won’t be able to,” Osatanakorn said at a morning briefing.

“We have to be 100% sure all kids will come out at the same time. Some might be ready before others. If they’re not ready, or it’s risky, we will not take them out.”

Mining disaster survivors say 'hard yards' lie ahead for trapped Thai group Read more

Authorities were sticking to their main plan of trying to drain enough water from the cave to allow the boys to be pulled out, he said, efforts that have been aided by an unseasonably dry day in Mae Sei.

“The most important thing is to lower water levels,” Osatanakorn said. “Water has decreased a lot but when it’s raining we can’t fight it. If it doesn’t rain we can have good results. Time is limited in getting the kids out.”

He said more water was currently being pumped out of the site than was seeping in and divers were working to seal holes in the rocks around the boys. But he declined to set a time frame for their evacuation. “It all depends,” he said.

Mermaid Subsea Services in Bangkok, a company that usually provides equipment for undersea oil and gas extraction efforts, has been in talks with Thai authorities to supply masks for any attempt to extract the children through the cave system. The company is sourcing AGA Divator masks – full face scuba models – that are specially fitted for children.

Facebook Twitter Pinterest Rescuer workers prepare small diving masks to deliver inside the cave. Photograph: Linh Pham/Getty Images

The boys will be dressed in wetsuits, boots and helmets, and divers will use an 8mm static rope that is already in place to guide them through the cave system, said Changkwanyuen.

It is unlikely the boys will carry their own 12-litre oxygen tanks – they are more likely to be provided the oxygen from a navy diver’s supply. In addition to this primary supply, fully filled “stage tanks” are also in place every 25 to 50 metres along the route, allowing the boys quick access to oxygen if their stocks are running low.

Chinese diver Zhou Yahui, who had just returned from the cave, said: “The water level will drop, but that doesn’t mean they won’t have to dive. It’s impossible to guarantee that.”

Hundreds of Thai soldiers and police are also being airlifted into the dense jungles above the cave system to scour for access points that might provide easier ways to access the children.

Any such discoveries might also allow authorities to drill directly into the cavern where the boys are sheltering, regarded as a potentially less risky method of extraction in contrast to forcing the children through a muddy, jagged cave system that is leaving some rescue divers with cuts and bruises.

Volunteer divers involved with the search for the boys said bringing them out through the cave if it started to rain was fraught with risks. “It’s not the easiest way and it’s definitely the scariest way,” said Claus Rasmussen, one of the international team working with the Thai navy.

Facebook Twitter Pinterest A Thai rescuer prepares oxygen tanks for diving after 12 boys and their football coach were found alive. Photograph: Sakchai Lalit/AP

“It’s a huge cave system, almost 10km long,” said Maksym Polejaka, another cave diver who spent five days leading Thai navy seals through the complex before the boys were found. When rains are heavy, most of the cave system is completely submerged, he said.

“You only have air pockets. You dive for 20 metres, then surface. Then you dive for 30 metres, then surface. The biggest passage you need to dive [takes] maybe 20 minutes.”

Rain also brings strong currents that slow progress dramatically and make swimming impossible, he added. “After the current becomes slower, you can swim, but hardly.”

Divers took more than three hours to reach the ledge where the boys are sheltering on Monday, but moving with the current on their return took about 50 minutes.

“The water level is stable now because hundreds of pumps are removing water and people are trying to block the sources. But if you stopped pumping, or if it rained, the water level would immediately rise,” Polejaka said.

Rasmussen said rescue options were being reassessed “on an hourly basis” as weather reports and water levels inside the cave changed. Even a small amount of rain would quickly flood the cave system and upend all the progress made so far to drain it. “[Rain] is the only thing that can truly upset what is going on, unless one of the kids gets sick,” he said.

As well as finding ways to extract the boys in the coming days, Thai navy seals are also planning for a scenario in which the rescue cannot take place, preparing to send food and medical supplies that could last the next four months until the monsoon subsides.

Thai soldiers conducted their first evacuation drill on Tuesday afternoon, locking arms to form a column from the mouth of the cave towards a field where 13 ambulances are waiting to ferry the group to hospital.

Mental health workers said one of them would be assigned to accompany each child in the ambulance along with one of the boy’s parents. The group have been inside the cave since 23 June, when they wandered inside after a football training session and are thought to have become trapped by rising water levels.

Additional reporting by Lily Kuo