The 12 Thai boys rescued from a flooded cave are seen cheerfully waving while recovering in their hospital beds in a heartwarming new video, as stunning footage of them being carried to safety is released for the first time.

The hospital video shows some of the boys making 'victory' signs, while appearing to smile from behind their green surgical masks in an isolation unit in Chiang Rai, northern Thailand.

The last remaining four school boys and their coach, who had been trapped in the Tham Luang cave complex for 18 days, were carried out on stretchers on Tuesday at the end of a 'miracle' three-day operation.

We're ok! Members of the Wild Boars football team are seen being treated at a hospital in Chiang Rai, their parents on the other side of a glass window

They do not look shell-shocked or stunned despite their harrowing stretch inside a dank, dark cave, followed by a risky rescue operation that was dubbed 'Mission Impossible'.

The youngest boy, 11, appeared asleep under a crisp white sheet while others, including their 25-year-old soccer coach, sit in bed.

Nurses are seen chatting with them and the boys respond with the customary Thai sign of respect - hands pressed together while bowing the head.

The video also sees some of their parents - who are still not allowed to touch, let alone hug, their sons due to the risk of infection - crying and waving to them from the other side of the glass windows.

The footage was shown during a press conference held by the rescue chief, acting Chiang Rai Governor Narongsak Osottanakorn, who praised the children as 'heroes'.

He said he believed the Wild Boar FC players would 'grow up to be good citizens', and added that they are 'healthy and strong'.

'Don't need to worry about their physical health and even more so for their mental health,' said Chaiwetch Thanapaisal, director of Chiang Rai Prachanukroh Hospital. 'Everyone is strong in mind and heart,' he said at the news conference.

Getting better: While some of the boys were lying down, others are seen sitting up and making gestures to the camera

Recovering: Some of the 12 Wild Boar FC boys are seen lying on hospital beds

Recovering: Video footage shown during a press conference shows the 12 young footballers in a hospital unit in Chiang Rai on Wednesday

The press conference also revealed that the order the 12 boys were rescued in was decided by their 25-year-old coach, Ekaphol Chantawong.

THAI CAVE BOYS 'SLEEPING' DURING RESCUE MISSION The 12 Wild Boar FC boys were passed 'sleeping' on stretchers through the caves, according to one of the former Thai Navy SEALs who took part in the mission. 'Some of them were asleep, some of them were wiggling their fingers... (as if) groggy, but they were breathing,' Commander Chaiyananta Peeranarong said. He added that doctors stationed along the dark corridors of the Tham Luang cave were constantly checking their condition and pulse. 'My job was to transfer them along,' he said, adding the 'boys were wrapped up in stretchers already when they were being transferred'. This is one of several reports of the children being 'drugged' or 'sedated' for the rescue. Earlier today, a Spanish diver said 'at least four' had been drugged. Fernando Raigal, who has 12 years of experience of commercial diving, claimed the rescuers had no other option. He told the BBC: 'The boys were sedated. They were unconscious [during the evacuation]. They were breathing but they were drugged.' This has been strongly denied by Thai authorities, including Prime Minister Prayut Chan-o-chau, who refuted sedation claims and added that had been given anti-anxiety medication, 'the same he takes to help him relax when he shoots guns'. Advertisement

It had previously been reported that the initial strategy of rescuing the strongest first had been changed before the rescue operation began, after a health assessment of the football players.

A specialist doctor visiting the group on the ledge deep inside the cave had determined that some of the weakest children may not make it unless they were brought out first.

Today, Navy SEALs commander, Rear Adm. Apakorn Youkongkae said the football coach had been the one to made the call.

'I haven't asked the coach yet why he chose that order,' he said. 'The coach was the one to choose.'

Their miraculous escape, during which the 12 boys were moved out one by one over three days, had seen them endure dives in zero visibility lasting up to half an hour, the leader of the U.S. contingent of the operation has revealed.

U.S. Air Force rescue specialist Derek Anderson detailed how parts of the rescue route would see the Wild Boar FC players put in a harness and high-lined across rocky caverns.

Anderson said the 12 boys and their coach, who were trapped for more than two weeks, were 'incredibly resilient.'

'What was really important was the coach and the boys all came together and discussed staying strong, having the will to live, having the will to survive,' he said.

The complicated operation to bring the boys out of the cave began on Sunday, when four were extracted.

Four more were brought out on Monday, and the operation ended Tuesday with the rescue of the last four boys and their 25-year-old coach.

Video shows the moment some of the young boys are being pulled out of the cave, carried on stretchers and surrounded by more than a dozen members of the 100-strong rescue team.

Wild boars: The football players made hands signs, which as well as being known as rock n roll sign of the horns means I love You in sign language, from their beds and appeared to be smiling from behind their surgical masks

Emotional: A mother is seen breaking down as she spots her son on the other side of the glass

Almost reunited: Parents are seen waving to their children in the isolation unit

Saved! All 12 players, pictured from top left clockwise, Adul Sam-on, 14, Panumas Saengdee, 13, Sompong Jaiwong, 13, Ekkarat Wongsookchan, 14, Pipat Bodhi, 15, Peerapat Sompiangjai, 16, Pornchai Kamluang, 16, Prajak Sutham, 14, Chanin Wiboonrungrueng, 11, Mongkol Boonpiam, 14, Nattawut 'Tle' Takamsai, 14 and Duangpetch Promthep, 13

The footage, released on the Thai Navy SEALs Facebook page, shows a complex operation with numerous divers - both foreign and Thai - using pulleys, ropes and rubber piping to haul the children to safety while seemingly sedated.

The 18-day ordeal riveted much of the world - from the awful news that the 13 were missing, to the first flickering video of the huddle of anxious yet smiling boys when they were found by a pair of British divers nearly ten days later.

The group had entered the sprawling Tham Luang cave in northern Thailand to go exploring after soccer practice on June 23, but monsoon rains filled the tight passageways, blocking their escape, and pushing them deeper inside in search of a refuge.

The shocking speed with which the rains would fill the cave soon also became clear to the international rescue team.

'The cave was dry when we arrived, and within an hour and half it had already filled up by 2 to 3 feet and we were being pushed out,' said Anderson said.

'That was just in the very beginning of the cave and at that point we realized this problem is going to be much more complex than we thought,' he said.

Sedated? One of the rescued boys is seen being removed from a stretcher and appears to be semi-conscious or possibly too weak to open his eyes

Rescued: A few seconds earlier he is seen seemingly grasping for one of the rescue medics while still wearing an oxygen mask

The footage shows a complex operation with numerous divers and rescue workers using pulleys, ropes and rubber piping to haul the children to safety

Another part of the video shows the team carrying one of the boys while the pipes used to pump out water are seen in the background

Here he comes! Members of the rescue team carry one of the 12 Wild Boar FC players after he is safely taken through the flooded tunnel system

One of the heroes: U.S. Air Force Master Sargent Derek Anderson talks about the risky operation of extracting the trapped boys and their coach

Dark route: A diver moves along the safety line used by the rescue team getting the children and their football coach out

Thailand's decision to dive the boys out despite their weak condition and lack of diving experience was made when a window of opportunity was provided by relatively mild weather.

A massive operation to pump water out also meant air pockets were created at crucial points of the cave, making a rescue possible.

Falling oxygen levels, risk of sickness and the imminent prospect of more rain flooding the cave complex for months meant 'the long-term survivability of the boys in the cave was becoming a less and less feasible option,' Anderson said.

Divers practiced their rescue techniques in a swimming pool with local children about the same height and weight as the members of the Wild Boars soccer team trapped in the cave.

The aim, Anderson said, was to make each of the boys 'tightly packaged' so divers could keep control of them and adjust their air supply as needed.

The process lasted hours for each boy, and involved them getting through long passageways barely bigger than an adult body.

Thai rescue teams arrange a water pumping system at the entrance to the flooded cave complex during the rescue mission to get the 12 boys and their coach out

Giant equipment: The giant water pump, which had been keeping the water levels down during the rescue, is being cleaned as the camp is being dismounted on Wednesday

Made it: Rescue workers are seen taking out the drainage system and machines after the end of the rescue operation

Rescued: A helicopter takes one of the boys rescued on Tuesday from the Tham Luang Cave near Mae Sai to hospital. Strapped to the stretcher, his head is held in a protective neck-brace and he is wearing sun-glasses shielding his eyes from the light

Buoyancy aids, hooded wetsuits, bungee cords and special face masks were carried by divers to the cramped patch of dry elevated ground where the boys were huddled.

The positive pressure masks were 'really crucial,' Anderson said. Their use meant that even if a boy panicked - perhaps because of getting snagged in a narrow passage - and got water inside his mask, the pressure would expel it.

Initial attempts to locate the boys were twice unsuccessful because of flooding of the narrow passages. Even as conditions improved, and divers began laying life-saving rope guidelines through the cave, it was perilous.

'In this type of cave diving, you have to lay line, rope, that's your lifeline. You have to ensure when you go in you have a way out,' Anderson said.

'They were making progress, but it was very little progress and they were exhausting themselves spending maybe five or six hours and covering 40 or 50 meters (yards).'

There were about a hundred people inside the cave for each rescue operation, Anderson said, and each boy was handled by dozens of people as their perilous movement through a total of nine chambers unfolded.

Chiang Rai province Acting Governor Narongsak Osatanakorn speaks to journalists during his news conference near Tham Luang cave complex on Wednesday

Brave: Some of the 12 children are seen in a video from July 2, when they were found after a week missing in the cave system in Chiang Rai

One team, one dream: Some of the players pose with their coach Ekaphol Chantawong, 25, after a football game some time before their cave ordeal which began on June 23

In some phases they were guided by two divers. In some narrow passages they were connected to only one diver.

In caverns with air pockets they were 'floated' through with the support of four rescuers. Some sections were completely dry but treacherously rocky or deep.

'We had to set up rope systems and high-lines to be able to safely put them in a harness and bring them across large open areas so they wouldn't have to go all the way down,' Anderson said.

Air cylinders placed throughout the cave were 'jammed' with 80 per cent oxygen instead of regular air because 'that would plus up their oxygen saturation levels and that would be really good for them, their mental state,' he said.

'The world just needs to know that what was accomplished was a once in a lifetime rescue that I think has never been done before,' Anderson said.

'We were extremely fortunate that the outcome was the way it was. It's important to realize how complex and how many pieces of this puzzle had to come together.'

'If you lose your cool in an environment like that, there is a lot of bad repercussions,' he said.