MARK WILLACY REPORTER: Saturday afternoon June 23rd.

Twelve boys and their soccer coach head into the rugged mountains of Northern Thailand for a trek.

They pose for photos before riding to the Tham Luang cave - a place they have visited before.

They are expected to return home to their nearby village later that day.

UPSOT REPORTER: A dozen members of a youth football team and their coach are missing ... after they entered a cave in northern Thailand

UPSOT REPORTER: A massive rescue effort is being launched.

UPSOT REPORTER: Investigators believe the teenage boys and their coach crawled into the cave and they never came out.

UPSOT REPORTER: Search and rescue crews are on the scene trying to locate the boys

UPSOT REPORTER: It's believed the team has been trapped by a flooded stream near the cave entrance.

MARK WILLACY REPORTER: Within 24 hours of the boys going missing, a search operation is underway.

The boy's bikes and backpacks are found near the entrance to the cave, which becomes ground zero in the search.

Distraught family members gather.

UPSOT MOTHER OF MISSING BOY [THAI]: My son, come on out. I am waiting for you here.

UPSOT MOTHER OF MISSING BOY [THAI]: Please hurry up and come home. My son, let's come home together.

UPSOT MEMBER OF RESCUE TEAM [THAI]: It's up to the Navy SEAL team to find them. We suspect they are still in the cave alive.

UPSOT NAMHOM BOONPIAM, MOTHER OF MISSING BOY [THAI]: I hope they are safe. I still have hope. I hope that all 13 boys will come out safely.

MARK WILLACY, REPORTER: The Tham Luang cave is a 10-kilometre long limestone cave system with deep recesses and narrow passageways.

Most of the year it's relatively dry, but when the monsoon comes it quickly fills with water and when that happens the caves become impossible to enter or leave.

The water levels are now rising and the boys cannot swim.

The night after the boys are reported missing, the Thai Navy's elite SEALs diving team join the search.

Working around the clock, in pitch darkness, they wade, swim and dive through the black waters.

At the same time, agencies and volunteers begin the mammoth task of pumping water from the cave and surrounding area.

UPSOT VERN UNSWORTH, CAVE EXPERT: If they're in the right place they can survive for 5-6 days.

But the water now, the floodwater, is getting higher and higher, so there will be a point in time where this cave here, even the entrance will close.

MARK WILLACY REPORTER: By day three, the search has escalated into a major military operation.

Hundreds of searchers scour the mountain for alternative entry points into the cave.

UPSOT RESCUE WORKER [THAI]: One of the holes we explored today was about 600 or 700 meters in depth vertically.

But there are floors on the way descending through that depth.

MARK WILLACY REPORTER: The hope is the boys and their coach have made it to a location clear of the rising water.

CHALONGCHAI CHAYAKAM, DEPUTY COMMANDER THIRD ARMY [THAI]: We still haven't reached the target area in the third hall in the cave that everyone calls 'Pattaya Beach'.

To dive through the water each oxygen tank can take us through only 200 metres but the distance is several hundred metres.

We'll keep on going by rotating the workforce. We are not going to stop.

All the relatives can do is pray.

UPSOT BRAHMA PRIEST, CHIRASIT PLOYDAM [THAI]: We pray asking for the safety of the children because we believe the children are still alive.

MARK WILLACY REPORTER: After four days, there's still no sign that the boys are alive.

The Thai navy SEALS are unable to navigate the labyrinth of tight passages filled with murky floodwater.

Thai authorities call for international help.

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: Yeah so it was a Wednesday morning.

I was still at the house.

It was about 5:45 in the morning, and my director of operations, uh, my number two guy in the squadron called and said, "hey, sir, I'm sure you're tracking that there's a soccer team stuck in a cave in Thailand.

Uh, be ready 'cause we're being notified that we might, uh, head out."

And, uh, and I thought, "Awesome. That's exactly the type missions that, uh, we want to be called up for.

CAPTAIN JESSICA TAIT, U.S. AIR FORCE PUBLIC AFFAIRS OFFICER: The next thing I knew, you know, we're all loading onto an MC-130.

Uh, it's one of our aircraft and we're- we're flying to Thailand.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: Landed about one o'clock in the morning on the 28th of June, and then, uh, key leadership pushed straight to the cave site.

CAPTAIN JESSICA TAIT, U.S. AIR FORCE PUBLIC AFFAIRS OFFICER: So we go into the cave, and it was completely dark.

And like I'm walking in thinking like, this is so surreal.

I mean it's- it's so dark.

A few of us had headlamps.

I did not, so I'm trying to tag along as close as I can to some of the other members of the team.

But I could just sense like, oh my gosh, there's like 12 children and a coach in here, and I'm just in the entrance way, and I'm spooked out.

I can't even imagine.

MARK WILLACY REPORTER: Two British cave divers have also been called in by the Thais.

Rick Stanton and John Volanthen are considered the best in the world and are the first to dive deep into the cave.

They brief the Americans on the daunting task ahead.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: The technical experts from the United Kingdom, they had begun diving much sooner than us, and uh, getting their feedback was also invaluable.

You know, those were when the rain levels were the highest, and they were saying, "Hey, you know, in cave diving, you, you have to be able to lay line, you have to be able to have a way out, if you're going in," and they were saying, "the currents right now are not manageable, you know, we've battling, trying to move forward.

The rains are still falling, the flows are getting higher, the visibility is zero, the water's cold, like, let's, let's take a minute, everybody take a deep breath and let's come at this from a collective perspective of how can we tackle a really complex problem, that I think over the next few days and even weeks, we realized, like, has never been done before.

MARK WILLACY REPORTER: On Sunday July first, a break in the rain allows the rescue dive team to set up a base inside one of the cave chambers.

The British divers forge deeper into the cave.

Far below the surface they swim against strong currents for 1.5 kilometres.

And then the moment that seems like a miracle.

UPSOT DIVER: We found them, we found them.

MARK WILLACY REPORTER: Almost 10 days since they first entered the cave.

DIVER: Raise your hands.

BOY: Thank you. Thank you.

DIVER: How many of you?

BOY: Thirteen.

DIVER: Thirteen?

BOY: Yeah, yeah.

DIVER: Brilliant.

No, not today. Just two of us. We have to dive.

BOY [IN THAI]: Diver says not today.

DIVER: We are coming. It's OK. Many people are coming.

DIVER 2: Many, many people.

We are the first. Many people come.

BOY: What day?

DIVER 1: Tomorrow.

DIVER 2: No, no, no, what day is it?

They are asking. Monday. Monday.

OK, but one week...uh, Monday.

You have been here for 10 days.

You are very strong.

BOY [IN THAI]: Who knows English? Translate for us.

BOY 2 [IN THAI]: I can't catch up with the words.

DIVER: Lets go up, ok go back, we come, we come.

BOY: We are hungry.

DIVER: I know, I know. I understand.

We come, ok, we come.

BOY 1 [IN THAI]: Go up the top together.

They will take our photos first.

BOY 2 [IN THAI]: Tell them we are hungry.

Boy [IN THAI]: I've told them. They know.

What day you come to help me?

DIVER: We come here, we have been diving here for what...tomorrow, we'll help tomorrow.

DIVER 2: The Thai Navy, the Navy, Navy SEAL will come tomorrow.

With the food, the doctor and everything.

Today, a light? You have a light. We'll give you more light.

DIVER: You go up, Ok? Up, up.

BOY [THAI]: Come up. Brother, rush up.

DIVER: That looks fun!

BOY: Yeah, yeah. I am very happy.

DIVER: We are happy too.

BOY: Yes, thank you so much. Thank you.

DIVER: OK

BOY: Where you come from?

DIVER: England, UK.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: Initially it's a huge sigh of relief.

Okay, the boys were able to find a high enough ground, they've survived this long, you know, with some of the higher flood levels in the cave.

But then it was, it was scary, because we realized how far back they were in.

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: There have been diving rescues that are done consistently and cave rescues that are done consistently, but cave diving rescues are very rare, and none of them have ever been done with 13 people 2.4 kilometres into the Earth.

MARK WILLACY, REPORTER, PTC: The families feel like their prayers have been answered, but it turns out the ordeal has only just begun.

The boys and their coach have been without food for a week.

They're tired and afraid.

The only way out is by diving. But as far as we know the boys can't even swim.

MARK WILLACY REPORTER: After locating the boys, the British divers Stanton and Volanthen call in reinforcements from home.

JASON MALLINSON, BRITISH CAVE DIVER: I'm a member of the British Cave Research Council Diving- Diving Team. So, um that's how I got called in. John and Rick came out first and they required extra assistance, so I was called in.

MARK WILLACY, REPORTER: And when you hear that it's 12 children and a young coach, they're in this situation, what's your first thought about the options or the viability of getting them out?

JASON MALLINSON, BRITISH DIVER: The first thought is they're not going to get out.

I mean the kids, we've done recoveries before with live people and it's all about panic under water.

Um you can't, you can tell a kid whatever you want, but in an actual situation where you've got a kid in the water, th-they're more than likely going to panic.

So, at first, we thought it's not possible to actually dive them out.

MARK WILLACY, REPORTER: Jason Mallinson's first dive into the cave confirms his fears.

JASON MALLINSON, BRITISH CAVE DIVER: You're swimming against the current on the way in.

So, usually on the way in, the- visibility is not too bad.

You're usually fine, the first diver.

But the first diver is finning, and that finning creates eddies in the water, which stirs up the silt.

And then the second diver doesn't get such a bad, ah such good visibility, and then the third diver gets even worse.

So, by the time you've got a fifth or a sixth diver in there, they're down to nil visibility.

And then when you get to the end of the cave and y-you turn around and come out, you're with the current.

So, anything that you stir up at the end of the cave is going to flow all the way out with you.

So, you tend to have a much worse visibility on the way out.

So, it's ah a bit of a sort of combat course on the way out, in sort of sometimes it's you can only just feel the line; sometimes you can see a, a foot in front of you.

Other times, it's just nothing, it's all by brail and you're trying to remember all these line traps.

So, it's quite a sort of mentally exhausting experience to go there and back.

MARK WILLACY, REPORTER: The unfolding drama is now a major international story.

Hundreds of journalists are here in a make shift muddy village at the foot of the Nang Non Mountain.

Thai people have also flocked to the site from all over the country to do whatever they can to help.

A 24-hour tent city in the middle of this remote location is feeding and supporting thousands of people involved in the operation.

Almost everything is being freely supplied.

ARCHIVE CAPTAIN JESSICA TAIT, U.S. AIR FORCE PUBLIC AFFAIRS OFFICER: Everyone coming here working long hours, hauling dirt, trying to feed everyone and volunteer their time and probably their money and their expertise.

MARK WILLACY, REPORTER: It's a sign that when the chips are down, I suppose people of many nations can come and work together.

ARCHIVE CAPTAIN JESSICA TAIT, U.S. AIR FORCE PUBLIC AFFAIRS OFFICER: It's beautiful to see that.

I can't even speak to the Thai leadership that we saw here in this operation, as well as to the people.

I mean, it's such a beautiful culture.

All the volunteers out there, you know, giving their time and their resources and never losing hope.

MARK WILLACY REPORTER: The operation has shifted from search to rescue.

A party of Thai Navy SEALs including a medic reaches the stranded boys, bringing food, water, heat blankets and medical supplies.

UPSOT RESCUER (THAI): Very good, everyone is very strong. They're coming but I don't know when.

Two fingers, two fingers.

MARK WILLACY REPORTER: Surprisingly they only have minor injuries.

UPSOT RESCUER (THAI): This will kill the infection first, then once you are out we will find you a beautiful nurse.

MARK WILLACY REPORTER: Waiting above ground, the boys' mothers are overjoyed as they watch the video of their sons.

UPSOT MOTHER [THAI]: I am so glad he is still alive and safe. I am speechless. I want to thank everyone who helped. Thank you very much.

UPSOT MOTHER [THAI]: I am dying to see him. I miss my son.

MARK WILLACY, REPORTER: What's it like diving up there and seeing all these kids huddled with their coach?

JASON MALLINSON, BRITISH CAVE DIVER: Um the first time, it was quite interesting, they all seemed you know in good spirits.

Um where they were was quite a desolate place.

Um they've nowhere to go but that chamber.

They've got to go to toilet there, they've got to eat there, so the smell is quite bad.

Um it's quite warm.

Um the first day with me and myself and Chris went through to orientate ourselves with the cave, we went and visited them and chatted with them.

Like you say, they had th-the four Navy SEALs in there, so they had somebody to sort of look after them.

We took them gifts in from the- well, letters and gifts in from the parents and we brought messages back.

So it was quite a good experience for them and for us to sort of you know pass on messages from the outside world.

MARK WILLACY REPORTER: While the nation and the world celebrate the boys' survival, rescuers grapple with the enormous challenge of how to get them out.

The search for alternative entry points to the cave has proved futile.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSOM, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: We were trying to find any other way, uh, because we knew the dive one was going to be the most dangerous to find a way to get these kids out.

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: We've had hundreds, if not thousands, of the Thai military that we were linked in with, and they're- they're not finding any other access points along the side.

And we found all the caving experts that we could, and they all confirmed no, that there's one way in and out of this cave, and that's at the front entrance of it.

There is no other option.

MARK WILLACY REPORTER: The mission could not be more dangerous.

The boys and their coach are a kilometre below the surface and 2.4 kilometres inside the notoriously treacherous cave.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: The hardest thing is just trying to portray, in words, you know, without physically being in the environment, like what some of these guys were up against, and talking to a lot of the experts, like, that do cave diving as a hobby, were like, "Man, this is one of the five most dangerous caves I've ever been in, in my career," and that was kind of, you know, the hair stands up on the back of your neck.

And then on top of that, we need to, we need to get a bunch of people out, and on top of that, the water's cold, and on top of that, it's muddy.

You, you have zero visibility so it's, everything is feel, uh, you know.

You might have to, uh, reach around and feel through different stalactites or rocks, uh, and then there's parts of the cave where the water really speeds up, you know, it goes from narrow to thin, and trying to fit through there, and to deal with some of those flows becomes very dangerous.

MARK WILLACY REPORTER: The option of leaving the boys where they are until after the monsoon season has been canvassed but abandoned.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: Some of the divers had an atmosphere monitor that was showing oxygen levels, uh, getting less and less, um, which is a huge concern for us, because one of the options was, "Hey, let's leave them in there for four months," so then that was not looking like the best option.

Then the food, alone, we were able to get, uh, with a group of, you know, Thai and British divers, some food back, but it was about a hundred meals.

But for 15 people, you know, 13 to 15 people, that, that wouldn't last very long.

And then just looking at, like, the cleanliness, the hygiene, if they were to have any sort of an infection, like, so a lot of those initial, "Let's maybe try to wait out this water, for three, four, five months," became kind of unrealistic courses of action.

MARK WILLACY REPORTER: Military engineers work through the night to install a kilometres long cable to deliver oxygen in to where the boys are stranded...but the idea is quickly abandoned as its impractical.

Pumps are in action draining water out of the cave but heavy rains are forecast, which could quickly submerge the entire system.

MARK WILLACY, REPORTER, PTC: This is just one of a number of pumps brought in to try to get the water level inside the cave down, some have come as far as the United States and without them the rescue attempt would be infinitely more dangerous.

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: The rain was still so much of a factor that every single pump was getting overwhelmed.

And we were fighting Mother Nature trying to, uh, get this much water out.

But it was really the understanding that the flow of water coming in and the lowering of the oxygen levels in Chamber Nine, that- that's- that's what kinda forced us to a decision of, "Hey, we've got to do something now."

MARK WILLACY REPORTER: A contingent of Australian police and army personnel has been on the ground since early in the search.

But it's two veteran cave divers from Australia who will play a critical role.

They were about to go on holidays.

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: I'm all packed up ready to go to a trip to the Nullarbor.

Harry and I were on the way the next day and so I had 45 mins to get to the airport so in that time I had to unpack everything that I had, reconfigure, and get the gear that I needed for this trip and go.

MARK WILLACY REPORTER: Dr Craig Challen is a recently retired Perth vet.

His friend 'Harry' is Dr Richard Harris, an anaesthetist from Adelaide.

They have dived together all over the world.

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: So we've been I contact with the British in days leading up to this, so we were broadly familiar with what was going on in the cave and yeah to be honest not looking good at all.

It's a long way in, most don't know how to swim let alone dive so we're all wondering how this is going to possibly work and to be honest the prospects are bleak.

MARK WILLACY, REPORTER: On Friday July 6, as Harris and Challen arrive at the rescue site, there is a tragedy.

News breaks that a former Thai Navy SEAL involved in the operation has died.

UPSOT SUMAN GUNAN, FORMER THAI NAVY SEAL [THAI]: I am getting ready to fly off to Chiang Rai.

MARK WILLACY REPORTER: Petty Officer Saman Gunan had left the navy but signed up to join the search as a volunteer.

Saman had been delivering air canisters along the route being used by the divers in the cave. In a cruel twist, he lost consciousness after running out of air himself on the return dive.

NARONGSAK OSOTTHANAKORN, MISSION COMMANDER: The mission failed yesterday.

The whole team felt sad yesterday.

The death of one person has affected our whole rescue team.

I felt sorry for his wife and child.

We need to try to prevent this kind thing from happening again and we will try our best.

This is why we need to keep testing our rescue plan until it is perfect.

MARK WILLACY, REPORTER: Obviously you hear about the death of Saman Gunan, the Thai Navy SEAL.

Does that reinforce the dangers, the risk of this mission?

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: There's no doubt that this is highly hazardous, not so much for us we can look after ourselves because this is what we do but for everybody else involved and the Thai navy divers - who are very highly capable guys but this is not the environment they're used to and that they are train for.

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: Yeah, that was obviously a very sobering moment.

We took a- a step back.

We took an operational pause.

We reassessed, uh, the risk that we were willing to accept.

And at the same time we realized, okay, this doesn't change anything. We still have 12 kids and a coach in there.

We still have to- to go forward and do this.

So as tragic as that event was, and in my mind he's absolutely a hero of the Thai people and of the world, um, it didn't slow us down any.

We...if anything our resolve was strengthened, and like, hey, we're not gonna let his loss, you know, be in vain.

MARK WILLACY REPORTER

In the aftermath of the tragedy, the mood of the rescue changes.

The short-lived elation after the boys were discovered has been replaced by a sense of crisis and grim determination.

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: Everyone else was starting to see the same exact, uh, logic trail that was very quickly becoming to the point that the dive option was the only option.

And the Royal Thai Navy SEALs were able to get an audience with the Minister of the Interior.

And they were able to do that because we feel like we had a pretty decent plan.

And when we went and briefed the Minister of the Interior, we just laid it out to him in a very logical sequence.

I told him that, "sir, the- the eyes of the world are watching us.

We've got 12 kids and a soccer coach that are trapped here.

We've got emotions at a, uh, a significant level here."

And unfortunately, in these type situations, emotions are not your friend. Emotions are not helping us to make sound decisions.

And I told the Minister of the Interior, "sir, we are looking at this only from a logical standpoint.

We are trying to remove all emotion."

But now we're getting to the point where we only had one option, and if we didn't make the choice to dive then the circumstances surrounding the situation would make the decision for us.

And I- I think they- they absolutely saw the logic of that, because very soon after that the- the Thai SEALs, um, told us, "Hey," you know, "It's approved. So we're- we're gonna go in and we're gonna do this."

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: At that point, we started to do rehearsals, you know, we did rehearsals of concept, where we would stage out exactly how we thought the cave was.

We would have water bottles as tanks and we would have them labelled and we knew that our chances would be better if we started doing non-standard stuff, like filling up a scuba tank, but putting 80% oxygen in it instead of standard room air.

And then we looked at the actual, will these full-face masks fit? Will these wetsuits fit? How are we going to have their flotation or buoyancy compensators, you know.

So, we had actual volunteer children and we, uh, the Thais were able to secure a pool at a school, and we went there and we actually dry rehearsed, where we had divers and children wearing the equipment they were going to use for the rescue, practice swimming underwater, practice handing them off, uh, going through all these details and trying to basically game out, to the best of our ability, what we could do to ensure that when it was actually, the decision was made and they said "Yeah, we want to enact this plan," that we could say that, to the best of our ability, we have rehearsed everything, collectively, as a community, and, uh, we're going to give ourselves the best shot, even though we know this is high risk.

MARK WILLACY, REPORTER: Did you have any role in preparing them for the journey out?

JASON MALLINSON, BRITISH CAVE DIVER: Yeah.

We'd get out of the water in the chamber and talk to them about what was involved.

We would get out and kit them up with the correct kit, because we had to bring the kit in from outside each day.

So, we'd have to bring a wetsuit in.

They'd get into the wetsuit.

We'd put them in a buoyancy jacket, um bring them down to the water, put them in the full-face mask and check that the seal was good and make sure they were breathing okay.

So, we were fully involved in the whole operation.

MARK WILLACY REPORTER: As preparations for the rescue move into their final stage, everyone's morale is boosted when letters written by the boys to their families, and brought out by the British divers, are released.

MARK WILLACY, REPORTER: Taking the messages back from the children out, that must've given you a good feeling, because this is the first sort of contact they've had?

JASON MALLINSON, BRITISH CAVE DIVER: Yeah, yeah, exactly.

I mean that was just impromptu.

Um nobody asked me to bring any messages out, but I had a wet notes pad, um which is a pad with waterproof paper, and I just thought, here you are, write a message to your parents, write it on this pad and I'll take it out.

So you know, we never knew what was going to happen.

We never knew that we were going to get them out.

So, I thought it was important at least for them to be able to send a message out to their parents, maybe just to put their parents' minds at rest to say, you know, I'm not doing too badly under the circumstances.

UPSOT (VOICE READING LETTER) Mum and dad, I love you ... If I can get out please take me to eat crispy pork.

UPSOT (VOICE READING LETTER) I am fine, it is a bit cold but don't worry. Please don't forget my birthday.

UPSOT (VOICE READING LETTER) I am happy, the SEAL team is taking care of us very well.

UPSOT (VOICE READING LETTER) I miss you all. I really want to get out so much.

MARK WILLACY REPORTER: And this from their devoted coach Ekkapol Janthawong.

UPSOT (VOICE READING LETTER) "Dear all parents, we are fine.

The rescue team is taking care of us very well.

I promise that I will take best care of the boys.

Thanks for all your support and I apologise to all parents.

Dear aunty and grandmother, I am fine, please don't worry about me too much.

Please take care of your health.

Please tell grandmother to make pork cracking with dipping sauce for me.

I will go and eat when I get out, love you all.

JASON MALLINSON, BRITISH CAVE DIVER: Where they were at that time at that moment, they were quite comfortable.

But it was only myself and Chris that knew what was coming in terms of the weather and, you know, in a few days' time it might not be so comfortable.

But obviously we didn't say that to them."

MARK WILLACY, REPORTER: What did you think of the way those kids behaved and comported themselves?

JASON MALLINSON, BRITISH CAVE DIVER: Really strong, really strong you know composure.

We told them about the plan, the vague details of a plan, that we'd have to- how we'd have to dive them out, and none of them were whimpering or crying or anything.

They just accepted what we were going to do.

Yeah, real mental strength from them, which was really surprising, considering their ages.

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: Its Saturday afternoon and Harry and I are going in to look at the boys and the coach and see what sort of state they're in and very pleasantly surprised about that, they're really keeping in good spirits.

They've got the 4 Thai Navy SEALs with them and they did a fantastic job of looking after the boys and keeping morale up - so everything was looking really good in there.

They have had a few days of being fed after their 9 days of no food and very little water so that aspect of it is good but some of them are pretty small and fragile - a couple only 30 kilos so they're tiny little things really.

They're starting to get cold after that time of exposure, its fairly warm in the cave 23 degrees but over time the dampness and the temperature eats away at you and they were starting to chill down - all they had were t-shirts and shorts so not much exposure protection.

MARK WILLACY, REPORTER: How was it decided who goes out first, who goes out in what batch? And when did the coach come out?

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: So, that was up to the ah, the boys and the coach and the Thai Navy.

We told them what was going to happen and said you choose your best men, and ah out they come. So, it was nothing to, to do with us. Um it wasn't

MARK WILLACY, REPORTER: Or strengths or weaknesses of the children.

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: Harry did not choose them, um as has been suggested. So, ah I think it was their bravest guys that came out first.

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: So the, the risk level was incredibly high, and in my mind the- the possibility, the probability, of success was about as low as you can get.

MARK WILLACY, REPORTER: So you thought there's no chance of getting the 13 out.

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: I didn't think that there was no chance, um, but when I was flat out asked, "What do you think the probability of success was?"

Uh, I told the governor I thought maybe a 60 or 70% chance.

So, I was fully expecting that we would, uh, accept casualties. Maybe three, four, possibly five, would die.

MARK WILLACY, REPORTER: It's now Sunday the 8th of July. The 12 boys and their coach have been trapped for 15 days.

The conditions are getting worse as the monsoon closes in.

There's a growing sense that it's now or never.

NARONGSAK OSOTTHANAKORN, MISSION COMMANDER: Today, we are at the peak of readiness.

It's D-Day.

At 10AM, 13 professional cave divers entered the cave to carry out the extraction of the kids, including five Navy SEALs.

They have been clearly briefed on how the extraction would be carried out.

MARK WILLACY, REPORTER: What about you, given your experience, in your own mind as a cave diver, were you 100 percent confident they'd all make it out?

How did you feel?

JASON MALLINON, BRITISH CAVE DIVER: No, the first operation...so, it was a three-day operation.

The first operation, like I was always confident we could get them out - it was getting them out alive.

UPSOT MILITARY ANNOUNCEMENT [THAI]: For those in the media and anyone not involved in the operation, we politely ask that you leave this area.

MARK WILLACY REPORTER: The Thai authorities order anyone not involved in the rescue operation to leave the area.

The media is moved 500 metres away from the operations centre.

UPSOT REPORTER: We are packing up everything

NARONGSAK OSOTTHANAKORN, MISSION COMMANDER: I confirm that all 13 children and coach are really ready health-wise and in good spirits.

All 13 are aware of our operation and they are ready for this.

They are ready to come out no matter what difficulties they may face.

MARK WILLACY REPORTER: As night falls a fleet of ambulances arrive...there's 13 of them, one for each of the boys and their coach.

The task of bringing the boys out will be the responsibility of a team of 13 foreign divers and 5 Thai Navy SEALs.

UPSOT: 'Be careful, ok?'

It will take them three hours to make their way through the narrow dark passages to reach the boys.

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: The main issue is - are these guys going to be taught to dive and dive out or are they going to come out as a package and we're going to do everything for them and its really, the former option wasn't going to be possible because of the language barriers and the fact that they're so young and so small, so they were going to have to have the whole thing done for them.

UPSOT CRAIG CHALLEN: So this is where the children are in chamber nine...there's a hill here.

MARK WILLACY REPORTER: Craig Challen will play a key role along the route of the rescue, but it is the unique skills of his friend, the anaesthetist Dr Harris, that will be critical to the success of the mission.

MARK WILLACY, REPORTER: And how are you keeping the boys calm?

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: Yeah so they did have some sedation to keep them calm because the worst thing that could happen would be one of those guys panicking and if you put me in a full-face mask with no previous experience and dragged me out of the cave, it's about a three hour trip then I would be terrified and probably panicking as well.

So um they were calmed down a bit

MARK WILLACY, REPORTER: Were they totally calm or...?

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: Yeah, yeah.

MARK WILLACY, REPORTER: So they were basically given an anaesthetic to knock them out?

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: Yeah, yeah, there wasn't much activity there.

MARK WILLACY, REPORTER, PTC: An official source has told 4Cs that Australian govt negotiated immunity from the Thai authorities for any Australian involved in the sedation of the kids just in case something went wrong.

MARK WILLACY REPORTER: The rescue operation is an incredible feat of planning and co-ordination.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: So, we kind of divided the cave up, to make it easier, into nine areas, right?

Nine sections, uh, the mouth of the cave and then you came down into one, uh, and then we had chambers one, two and three that were a little bit larger and more technical with ropes.

The really, really complicated spots were taken by British divers that were, you know, just extremely, 30 years plus of experience, um.

And we did that knowing that certain people have different strengths and expertises, and so that's kinda how we task organized the entire team.

And it was upwards of 150 people, you know, from chamber nine to the entrance of the cave, all working as one big team, with many different responsibilities.

JASON MALLINSON, BRITISH CAVE DIVER: My role was one of the what we call recovery divers.

So, I would take a kid from chamber nine and bring him the whole way out.

So, with the diving, we'd submerge with the kid.

And depending how the line laid, we'd either have them on the right-hand side or the left-hand side, either holding their back or holding their chest.

I have a face here, depending if we were likely to hit the roof or not.

Or if we could see what was going on, we'd hold them out a little bit further.

Swimming through ah the sump, the first day, reasonable visibility, I could see sort of a metre in front of me, so I didn't have to hold onto the line.

By the last day, it was nil visibility

So, it was much more ah mentally exhausting and I had to have the lad really close to me because if you didn't, you were bashing his head against the rocks.

Whereas if I had my head quite close to him and I extended my head above him, my head was bashing the rocks first, so we could- the visibility was that bad, you couldn't see the rock until you actually hit it.

So, each section of flooded section was ah a much slower process when the visibility was bad.

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: I'm one of the divers, so where the boys are there's a diving passage of about 350m and then they come out of the water, have to have all the gear taken off them, and get carried over some passage and get back into the water again that's about 200m or so over some rock piles and pulling them through a sump and so I was at that stage de-kitting them after that first small dive and transporting them across that, getting their full face mask, their dive gear back on and getting them sent off with the divers.

JASON MALLINSON, BRITISH CAVE DIVER: So, after the first flooded section, there was quite a long dry section.

We had guys there with a stretcher.

So, as soon as he came out of the water, he'd be into a stretcher and what we call a drag stretcher, so you can drag it along the ground to the next sump.

And so Harry would send them on their way, we'd dive in through the first flooded section where the drag stretcher was.

Craig would assess them, make sure they were ok for the next part of the journey, assess them through the dry section until they got to the next sump, give us the ok that it was ok to continue.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: There were certain areas that involved floating them, there were certain areas that involved diving them, swimming them, if we have two rescuers per child, you know, ensuring just that at all times, uh, if there weren't two, there was one always holding on to the child

MARK WILLACY, REPORTER: So you physically got a, a grip on the child, and you've got to then pass off to another diver.

It's, the visibility at terrible, and I suppose the pinch points are terrible as well.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: Oh yeah, absolutely.

And, and like I said earlier, it's not one section of the cave, it's like, there's also sections where uh, we had harnesses for the children, improvised harnesses, and it was huge, 150 sections of high line, where we would have them, you know, uh, placed uh, on the high line, and maneuverer across these very, very steep caverns, where we knew trying to walk them all the way down back into, into these muddy areas and, and tight areas would be real dangerous.

JASON MALLINSON, BRITISH CAVE DIVER: They had a full-face mask on.

So, it was basically that one thing that if the mask that they were using became dislodged and water entered that mask and it- couldn't get it out, that was the one thing that would kill them.

You got to a section, you know, th-the vertical section we was talking about, and by that time you've been in the system for five hours.

You don't remember where the vertical section is and the only time you find about it is when your head bangs against the wall there.

And you, you're trying to get yourself through this vertical section, but you can't remember exactly how it's laid out

So, I'm trying to get myself through it, but I'm also trying to get a kid through it, who's vert- sort of horizontally in the water.

Trying to post him through - no, that doesn't work; pull him back.

Trying to post myself through - that doesn't work.

And you could spend several minutes at one, just one obstacle to try and find your way through.

And you know, eventually we did it, but it's a very slow process and quiet, quite daunting.

MARK WILLACY, REPORTER: Did you feel in control the whole time or were there any moments?

JASON MALLINSON, BRITISH CAVE DIVER: I was in control in terms of I, I knew I always could get myself out.

I knew, as long as I didn't-the main thing is, you've always got to keep in contact with that guideline.

If you lose the guideline, you're in a lot of trouble.

So, I was confident of getting myself out, I was confident of not losing control of the line, I was confident of getting the kid out; I wasn't a 100 percent confident of getting him out alive.

Because if we bashed him against a rock too hard and it dislodged that mask and flooded his mask, h-he was a goner.

So that's why we had to be very slow and careful about not banging them against rocks.

NARONGSAK OSOTTHANAKORN, MISSION COMMANDER: After 16 days, today's the day we've been waiting for.

We are seeing the Wild Boars in the flesh now.

The operation today has been more successful than we expected.

The first boy came out through the chambers of the cave and exited at around 5:40pm Thailand time.

MARK WILLACY REPORTER: The news that the first four of the boys have been rescued and brought to safety is met with mixed emotions.

As the anxious families watch and wait to learn who has been saved, for some there is elation, for others more anxious waiting.

UPSOT RELATIVE [THAI]: I was wondering if he will be alright.

I told myself, he will be alright, I knew.

But I didn't say it out loud. I was worrying too, but I keep my feelings quiet.

I haven't been able to eat or sleep for some time.

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: It was a pretty hard day but we've had a fantastic outcome, they're all in hospital and they're doing well and we're trying not to get ourselves a false sense of comfort and it could all still go horribly wrong and it would be worst if we had good outcomes and then started to go wrong so we were still pretty toey.

At this stage everyone's been diving for multiple days and they're quite big days in the cave as well and so starting to get a bit tired and ready for a rest but we've got the pressure that we know the rain is coming.

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: My concern, uh, was that we would become complacent.

Because, yes, it wa- it was huge. I mean we just hit a home run.

Um, four for four.

You can't get any better than that.

Um, but in my mind the risk level didn't go down any at all.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: So it was a short celebration, and then right back to staying focused, you know, staying professional and ensuring that we continue to drive on, because we knew that that was just a small part, uh, a small success in an overall bigger mission.

And we knew that if, if the rain got to levels where it was before, that, uh, the rescue operation would probably come to an end, because it would just be too risky and, at that point, you're risking a lot of the health of the rescuers, too.

And so it was absolutely a race against time.

MARK WILLACY REPORTER: Less than 24 hours later, the seemingly miraculous feat is repeated.

After a second rescue expedition by a team of 18 divers another four boys are brought safely out of the cave.

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: After the second day when we had another four for four, uh, we pulled everybody aside and said, "This does not change a thing. We are not gonna lower our vigilance. We're not gonna lower our attention to detail."

If anything, I briefed to the UK dive team, "Hey, we've just gotten ... " after the second day, "we've gotten eight for eight. You guys are absolute rock stars. This is gonna go down in history."

MARK WILLACY REPORTER: With 8 of the boys out...only their coach and four others remain trapped.

The dive teams are regrouping, re-equipping, and re-energising...preparing for one final push...

MARK WILLACY, REPORTER, PTC: We have just heard in the last hour or so that the 9th and 10th boys have been brought out and the news just coming through now is that the 11th boy is in the cave with two divers being ushered through the narrow corridors.

MARK WILLACY REPORTER: The eleventh boy soon emerges and there's news the coach is also free.

As night falls only one boy remains inside the cave.

Three Thai Navy SEALs and the Australian doctor, Richard Harris are with him - they will stay until the very end.

MARK WILLACY, REPORTER: Obviously being an Australian, I should ask you about Harry Harris. How did he perform?

JASON MALLINSON, BRITISH CAVE DIVER: Brilliant, really.

He was the lynchpin of the whole operation.

Without him, we wouldn't have been able to do what we did, his bedside manner when he was there with the kids and that, talking to them, calming them down and stuff like that, he was the one that sort of sent them on their way and we were just the transporters.

So yeah, he was the, the lynchpin of the operation.

MARK WILLACY, REPORTER, PTC

The news is out unofficially at this stage that all 13 members of the Wild Boars soccer team are out of the cave. That this has been an unrivalled success that this is a miracle rescue.

MARK WILLACY REPORTER: The 18-day vigil is over.

MARK WILLACY, REPORTER: Five out the last night. It's an amazing story. How did you feel when you finally got that last, that last member of the team out?

JASON MALLINSON, BRITISH CAVE DIVER: Quite emotional, you know?

As we were getting closer and closer to the entrance, I got quite emotional.

I don't normally, it's just what we were doing was to come out.

And I've got a kid myself now, so it was quite a good feeling.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: When, you know, you had the last group of people come out, and then we knew all four Thai SEALs came out, and everybody was all standing there, around, you know, 10 o'clock at night, and we actually took a moment and let the emotions come back in, and I think that uh, it really hit, kinda hit you in the feels, and we were like, "Man, we just accomplished something.

As a huge team. It took all these different people coming together, um, and I think that the world was watching, one way or another, you know.

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: Enormous sense of relief um and this is when it's good for the divers because we get to just walk out of the cave and ah go home.

Um everybody else still had a lot of work to do. The Thai Navy guys still had to swim out, so they were another two to three hours behind.

MARK WILLACY REPORTER: The soccer team is safe but there's a final moment of drama for the rescuers still inside the cave.

MASTER SERGEANT MASTER SERGEANT DEREK ANDERSON, U.S. DIVE OPERATIONS COMMANDER, U.S. DIVE OPERATIONS COMMANDER: Yeah, I don't know if it was kind of a supernatural intervening, but one of the pumps back at chamber three failed, and we had a fair amount of guys out there, waiting for the last group of SEALs to come out, you know.

Uh, and we got the call, "Hey, water levels are rising fast that was definitely a spike of adrenaline towards the end of the night.

MARK WILLACY REPORTER: For the Thai authorities who led this mission it is a dream result.

NARONGSAK OSOTTHANAKORN, MISSION COMMANDER: After Team Thailand, team government officials, private industry team, and the media team that helped us, including the support from the whole world, we did something nobody thought possible.

It's the first time in the world. It is our pride - mission possible of team Thailand.

MARK WILLACY REPORTER: The twelve boys and their soccer coach are recovering in hospital, still seemingly unaware that the whole world has been watching.

CRAIG CHALLEN, AUSTRALIAN CAVE DIVER: We went to the hospital to see them yesterday, which was a really good experience.

And yeah, they're sitting up and happy and ah eating.

Words cannot describe how happy we were.

Yeah, um it- honestly, it was not a result that we thought we would get.

We were ah, you know, w-we thought there was a very real prospect that we would be doing body recoveries, rather than um live patient extractions from there.

Um and you know, as I say, I'm still pinching myself a little bit, wondering if that's really what happened. It does seem too good to be true now.

CAPTAIN JESSICA TAIT, U.S. AIR FORCE PUBLIC AFFAIRS OFFICER: I remember when we were first here and some of our, you know, our tough guys were saying like, "I don't even know if I could survive, like, these are kids."

And for me it's like, it just showcases these children's will to live.

Um, as well as to, you know, the coach that provided that guidance and yeah, I mean these are some brave individuals, and I really do know that they're going to go down in history for the courage they showed.

JASON MALLINSON, BRITISH CAVE DIVER: It's one of the most difficult and dangerous and risky things I've ever done, not in terms of my own personal safety, but in terms of the people I was responsible for.

I've never done anything as risky as that and I don't think I ever will again.

But it was the only option we had, and we took it.

MARK WILLACY, REPORTER: In a world full of bad news, how good is this?

MAJOR CHARLES HODGES, U.S. MISSION COMMANDER: This is awesome.

I mean we're so incredibly overjoyed that not only is it a good news story, but at the end of the day we got the kids back together with their parents, and that's what matters in my mind.