NOVA

In Thailand...

A flooded cave...

12 young boys and their soccer coach

trapped somewhere inside.

With monsoon season just beginning,

and water levels rising,

time is running out.

They were moving so much water out of there.

The problem was, it's like turning the faucet on

and trying to siphon water out at the same time.

As an international team of elite divers

searches miles of submerged passages,

the whole world watches in suspense and wonders...

In Thailand, there is a very concerning situation.

"Can the boys still be alive?"

We came back to some pretty horrifying news.

But then...

How many of you?

They're all alive.

13, brilliant.

Now an impossible decision looms.

How to bring 12 children out...

The only option we had was to go with the diving option.

...through some of the most dangerous diving conditions

in the world?

Even the professional cave divers said,

"This is some of the sketchiest diving we've ever done."

You couldn't see your finger

in front of your face until you touched your mask.

A desperate mission begins.

Panic usually leads to instant death.

"Thai Cave Rescue,"

right now, on "NOVA."

Major funding for "NOVA" is provided by the following:

It was a nightmare that gripped the world.

A stunning display of courage and technical prowess

in the face of life-threatening danger.

The miraculous rescue

of these 12 young boys and their soccer coach

from one of the deadliest environments on Earth...

A flooded cave.

The Tham Luang cave in northern Thailand.

Well, this is it, Tham Luang.

It's a popular destination

for day-trippers and adventurous locals.

In the dry season,

explorers plumb its twisting depths.

The cave is located within the Doi Nang Non mountains.

It winds for an incredible six miles,

a limestone labyrinth of tight passageways

and expansive chambers.

Saturday, June 23, 2018.

12 young soccer players and their coach

venture inside the cave,

a trip to celebrate a boy's birthday.

But soon after, the skies open up,

and a powerful monsoon storm strikes.

In Mae Sai, where the boys live, a rainy night has descended.

Beginning to worry, parents start calling around

and gradually learn the boys have gone to the cave.

When they travel there,

they are met by an alarming scene.

Bicycles locked to a fence,

along with abandoned soccer cleats.

Worse, water is rushing into the cave,

with no sign of the boys.

Officials are on the scene,

and, realizing the boys may be in mortal danger,

some parents enter the cave.

Among those desperate to find them

is Mr. Bandit Phanphalakorn,

a close friend of one of the boy's fathers.

I went in a short distance,

but didn't dare go any further.

But one of the boy's fathers continued with the rescue team.

He went on for about an hour and a half,

but started to have breathing difficulties,

so had to return.

It's now 1:00 a.m.,

and the boys have been missing for half the night.

But where are they?

What's happened to them?

Fearing the worst,

local governor Narongsak Osottanakorn

makes a tough call.

From that Saturday night until Sunday,

we realized we couldn't do anything much

about the situation.

So we decided to stop the operation,

to rest and collect new crew and equipment.

If the boys are somehow still alive,

deeper in the cave,

they'll have to spend the rest of the night on their own.

But as heavy rain continues,

can anyone really rest as water levels continue to rise,

and not just at the entrance?

The intensified rainwater is pouring

into a deep, underground stream north of the cave,

causing water to flow furiously down the northern passage,

trapping the boys somewhere within the subterranean maze.

To make matters worse,

water is also entering from the south,

while the groundwater below is thought to be rising,

flooding the cave in many low-lying areas.

I was very worried.

I didn't eat, didn't sleep much, either.

I slept two to three hours, because I was thinking,

because everyone was thinking as if your own son was missing.

The next morning,

officials confront a daunting question:

If the boys spent a terrifying night in a dry part of the cave,

how can they be reached?

From the entrance, it's impossible to tell

how badly flooded the rest of the cave is.

To aid the search, professional cavers arrive.

You see where, you see where it comes down like this.

Among them is the first foreign rescuer,

British caver Vern Unsworth.

If we can get up there... Mm-hmm.

We can virtually get to the GPS point

and then do a search.

Having spent years exploring the Tham Luang cave system,

Vern's knowledge of its layout is vital to the search mission.

Up on the mountain, he leads a team hunting

for alternative access points into the cave.

Another caver to arrive is Noppadon Uppakham.

This is one of the most challenging rescues

he's attempted in a flooded cave.

The rain was quite a major obstacle,

because if the rainfall increased,

we didn't know how much water would enter the cave,

which could be dangerous for anyone searching inside.

Cavers quickly discover that in some places,

water is up to their necks.

And farther along,

it has risen all the way to the ceiling.

It's now obvious

that if the boys are going to be found alive,

qualified scuba divers with cave experience are required.

But how quickly can they be brought to the scene?

The governor calls in Thailand's most formidable fighting force,

the Thai Navy SEALs.

Like American Navy SEALs,

they're an elite branch of the navy

that takes on the most dangerous missions.

With them is Dr. Pak Loharachun,

a highly trained diver and experienced doctor

of the Royal Thai Army.

I had worries

because we didn't know the conditions inside the cave,

and crucially, we didn't know exactly where the kids were.

At that moment, the rescue was at a critical stage,

as the water was torrential.

The rescuers need to make a guess

about where the boys are.

Luckily, there are some maps of the cave,

produced in the 1980s by French cavers.

No one knows how accurate they are,

but from what can be pieced together,

the interior looks like this.

The cave system is thought to be about six miles long.

A daunting distance,

but such a long cave offers the hope

that there are plenty of places

dry enough for the boys to retreat to

and flee the rising water.

One section, called Pattaya Beach,

looks particularly promising,

as its elevation suggests

it may have stayed dry during the flooding.

But Pattaya Beach is about one-and-a-quarter miles

from the flooded cave entrance.

That might mean swimming a vast distance underwater

in tight spaces

and pitch-black, murky conditions.

The SEALs team started work immediately

when we were first told to look for the kids.

Each day, we tried to go as far as possible inside the cave.

As is normal protocol, the SEALs lay a guideline

so they can find their way out again.

In zero visibility, a guideline is a lifeline.

The SEALS brace themselves

in preparation for what they might find.

They push as far as they dare,

but their air supply is too limited.

Thankfully, they find no bodies.

But that means the boys must be even deeper inside.

Meanwhile, the water continues to rise.

Rescuers try to stabilize levels by draining as much as possible

using heavy-duty pumping equipment.

But despite the rescue efforts,

water levels inside the cave aren't decreasing.

And rescuers worry

that Pattaya Beach may already be flooded.

But they know the cave continues

for a long way beyond that point.

So they can only hope the boys were able to move

even farther into the cave.

But now, after more than 72 hours,

the boys would be facing other serious problems.