NARRATOR: A pleasure cruise turns deadly.

The Costa Concordia smashes into the rocks off the coast of Italy.

32 lives are lost.

FRANCO PORCELLACCHIA: It is something that you could never imagine that can happen.

It's like a nightmare.

NARRATOR: In the wake of a horrible human tragedy, another disaster looms.

A ship the size of a town threatens to break up just off shore, wrecking an underwater haven.

NICK SLOANE: She's very finely balanced, and if you disturb that balance, she goes into deep water.

NARRATOR: Battered by wind and waves, it's a ticking time bomb.

RICH HABIB: This job has such large ramifications.

All the chips are on the table.

NARRATOR: Now an international team of engineers and divers faces a daunting challenge: to raise the massive shipwreck and tow it away in one piece.

SERGIO GIROTTO: It's something that has never been done, has never been attempted.

NARRATOR: Can this mangled, fragile wreck the length of three football fields and weighing 45,000 tons be wrenched off the rocks without splitting apart?

Any movement?

MAN: It's a little bit heavy.

NARRATOR: "Sunken Ship Rescue," right now on NOVA.

♪ ♪ NARRATOR: The island of Giglio, an Italian vacation paradise, famous for its clear Mediterranean waters and pristine coral reefs.

But just off shore lies something that could spoil anyone's holiday.

(boat horn honks) A rotting shipwreck, a reminder of a tragic maritime accident.

January 13, 2012.

The Costa Concordia sets sail from the port of Civitavecchia en route to the city of Savona.

On board, 3,200 passengers and 1,000 crew members.

(applause) That afternoon, the ship's captain makes a fateful decision.

He decides to divert the ship to the island of Giglio, sailing along the coast, close to shore.

With the vessel traveling under manual control, she crashes into an underwater reef.

(loud scraping) We heard a very unusual kind of grinding sound.

Almost like fingers- on-a-chalkboard type of thing.

(scraping continues) (loud banging) NARRATOR: Seawater floods inside.

MEGAN MAURI: When I saw the water starting to seep in, I ignored it at first.

Like, that just doesn't happen.

That doesn't happen on your honeymoon, and it's not possible in this day and time that a huge cruise ship like that could sink.

NARRATOR: But it was possible.

As the ship starts to capsize, passengers flee for their lives.

Plates were moving.

Silverware was jingling.

(dishes clanking) It just kind of sunk in, "This is for real."

NARRATOR: Shortly after midnight, the vessel keels over and crashes onto the rocks.

NANCY LOFARO: We looked over the rail.

MARIO LOFARO: The ship is leaning, and it's leaning more and more.

We knew this was so serious.

NARRATOR: It's the biggest maritime evacuation in history, and a human tragedy.

32 people are killed.

The captain is charged with abandoning ship and manslaughter.

But that terrible night is not the end of the disaster.

After the search for survivors ends and the last rescue workers have left the island, the colossal ship remains, half-sunk right off the coast.

The vessel's owner, Costa Crociere, faces a salvage challenge of epic proportions.

The ship is three football fields long and 13 stories high.

She's filled with half a million gallons of fuel oil and supplies for several thousand people.

If she breaks up, she will spill her contents into the pristine Mediterranean waters.

To figure out how to remove the wreck, the ship's owners send in one of their top men, Franco Porcellacchia.

Franco knows the Costa Concordia better than anyone because he helped to design her.

PORCELLACCHIA: I am a naval architect and marine engineer.

I was in charge of the construction of this vessel in the old days.

It is very sad.

It's something that you can never imagine that can happen.

It's like a nightmare.

NARRATOR: Franco's concerned that this human tragedy doesn't turn into an ecological disaster.

The vessel crashed in a place of outstanding natural beauty.

The sea around Giglio is a protected area for dolphins and whales.

It's full of stunning corals, rare fish and sea grasses... and an endangered giant mussel growing up to three feet long.

PORCELLACCHIA: Our commitment was to restore the situation and to give back the island to the people living in the island, creating the least damage possible to the environment.

NARRATOR: Two weeks after the disaster, salvage divers tap into the hull to start pumping out the oil.

But the wreck itself remains an environmental time bomb.

Full of rotting food, cleaning chemicals and plastics, if it stays on the rocks, it could leach pollution for decades.

The cruise line calls in Rich Habib, managing director of the American company Titan Salvage, to figure out how to remove the wreck as quickly as possible.

RICH HABIB: In the old days, we salvaged ships or wrecks for the value that we could get out of the materials, or we moved them because they were blocking a navigational channel.

Nowadays, salvage is really done for environmental reasons.

The Concordia, it's an environmental hazard to the area, and it has to be removed.

NARRATOR: Rich must find a way to remove the ship without further damaging the environment.

One option is to cut the vessel into smaller pieces, taking it away bit by bit.

To do this, Rich's crew would need to anchor platforms either side of the wreck.

(splashing) Between them, they would stretch a wire with an abrasive coating almost as tough as diamond.

Powerful winches would then pull the wire back and forth, driving it through the hull, slicing the ship into manageable pieces which they can then tow away.

Engineers have used this technique before to remove the wreck of the Tricolor cargo ship.

The vessel, which was carrying 2,800 new cars, sank off the coast of France in 2002.

It took nearly two years to dice the ship into nine pieces and tow them away.

The Costa Concordia is twice the size of the Tricolor.

Cutting the ship up would not only take longer, but would spill its contents into the sea, polluting the surrounding water.

HABIB: There's a couple of problems.

First of all, there's environmental issues, and secondly, there's technical issues.

The vessel's laying on its side, so you'd have to cut at an angle through all these decks and all these bulkheads.

I mean, just aside from the mess you're going to make, there's just no practical way to contain all the debris that's going to occur.

So I don't think cutting it up is practical, and it's not the right thing for this place.

NARRATOR: To reduce the danger of pollution, Rich must find a way to remove the wreck intact.

Inspiration comes from an unusual source.

In 1941, one of the victims of the Japanese attack on Pearl Harbor was the battleship the USS Oklahoma.

Up to nine torpedoes tore a 250-foot-long hole in the ship's hull.

Water flooded inside, rolling it over.

More than 400 sailors were on board.

Only 32 survived.

To clear the harbor, military engineers needed a way to haul the 27,500-ton vessel upright.

They planned a bold operation, using cables and winches.

First, they dropped 2,200 tons of coral along her bow to pin the ship in place.

Then, they bolted wooden frames onto the hull.

They attached high-strength steel cables running through a network of pulleys and hooked them up to powerful winches made from streetcar engines anchored in concrete on the shore.

By pulling steadily over three months, the salvage crews gently rolled her upright.

They call this technique "parbuckling."

HABIB: Well, the Oklahoma, she weighed about 30,000 tons.

The Concordia weighs about 45,000 tons, and that's without absorbed water and other things we need to count, so while the technique is not new, the magnitude of it is just off the charts.

NARRATOR: Parbuckling is not easy.

An attempt to right another Pearl Harbor wreck, the USS Utah, ended in failure.

Instead of staying in position and rolling upright, she slid out of control.

She's still lying there today.

Despite the risk, Rich and his team plan to use parbuckling to right the Costa Concordia in one piece.

Morning, guys.

NARRATOR: To give his plan the best chance of success, Rich brings in one of the world's top salvage experts to direct operations.

Zambia-born master mariner Nick Sloane has salvaged more than 80 ships, tankers and oil rigs in a globe-trotting career spanning 34 years.

At twice the size of the Titanic, the wreck of the Costa Concordia will be his most challenging project to date.

SLOANE: The size of the ship and the location, that makes it more challenging than anything that has been done before.

And it's just the scale of it, the components, the engineering.

NARRATOR: With a vast team of engineers, divers, welders and technicians from 26 countries, Nick knows he must remove the ship as quickly as possible.

A delay of even one day will be expensive.

SLOANE: We don't like delays.

So when we have 500 people on the project plus all the equipment, it's a million dollars a day.

NARRATOR: But an underwater survey of the wreck site immediately reveals a major problem.

SLOANE: If you see the profile of Giglio from the top up by the castle, it's a 35 to 45 degree slope that she's on.

And what you see underwater is these two little ridges that she's balanced on, and if you disturb that balance, she goes into deep water.

NARRATOR: The wreck balances precariously on a rocky ridge.

The fear is that strong waves could send her crashing into deep water, making salvage virtually impossible.

So before the crew can even begin to salvage the ship, they must secure it to the ridge.

They'll drill anchor blocks into the rocks and run 16 high-strength cables under the keel and thread them through jacks bolted to the hull.

This giant cradle of steel will hold the ship secure to the seabed as the team prepares for the epic task of raising her off the rocks.

Nick is racing against time.

He has only five months before the winter storms roll in.

All right, let's do it.

NARRATOR: Experts arrive from all over the world along with a rig to start drilling the holes for the anchor blocks that will hold the ship in place.

Each block must be secured with ten steel tendons plunging as deep as 50 feet into the rock.

Though fragile coral reefs lie nearby, the seabed under the ship is hard granite, making drilling a difficult process.

(drill whirring) By now, Nick had hoped to start installing the equipment for parbuckling the ship, but the anchor blocks are still not ready, and the weather could turn bad any day.

SLOANE: The weather's always your worst enemy in a salvage operation.

We had waves going straight over the red lighthouse.

And in fact in 2008, that whole breakwater was destroyed.

So it gets pretty nasty out here, and that's our worst enemy, especially this time of the year.

NARRATOR: An early winter storm could knock the ship off the ridge.

I still think we've got our work cut out for us.

This will take a bit of time.

NARRATOR: It takes six months for divers and technicians to secure the four anchor blocks.

Tied to the metal anchors, a cradle of steel cables finally hugs the ship tight against the seabed, preventing it from sliding into deeper water.

The vessel is now secure.

But there's one more task to complete before the team can begin salvage work.

PORCELLACCHIA: This is a beautiful area, and there are special inhabitants here.

In particular, in this part of the island lives a colony of giant mussel.

NARRATOR: The ship has crashed almost on top of a bed of rare giant mussels.

The species Pinna nobilis used to be harvested for food, but is now protected.

Before they can move the ship, they must remove the precious mollusks and replant them away from the wreck.

PORCELLACCHIA: Altogether, I think it was more than 100 of them, and they are still alive.

I'm sure that they will like where they are now.

(laughing) NARRATOR: With the mussels safe in their new home and the Costa Concordia secured to the bedrock, the team can finally start work on the ambitious scheme to parbuckle the ship.

This is the plan.

First, they must build a huge platform under the ship to support her hull as she rolls.

They'll fit massive tanks filled with air to her port side.

On top of the tanks, a battery of powerful jacks pulling on a bank of steel wires.

As the jacks pull, the air tanks will act like giant water wings to cushion her descent as she rolls down into the water.

Only after the ship rests upright on the platform can the team refloat her and tow her away.

HABIB: If you plan a parbuckle wrong or it misfires on you, we will have much more of a problem than we would have had to start.

NARRATOR: First task: build the giant underwater platform to catch the Costa Concordia as she rolls upright.

Made from 5,000 tons of steel, the six sections of platform will cover an area the size of a football field.

Constructed in shipyards across Italy, the giant pieces will be towed by tugboats to the crash site.

Here, a powerful crane will need to maneuver each section onto its foundations, which have to be drilled into the rocks with extreme precision to make sure the platforms are level.

Pioneer, Pioneer, Pioneer, mobile one.

NARRATOR: In Giglio, a large floating barge arrives, providing extra accommodation as the underwater crew grows to 120 divers.

They have one of the most difficult and dangerous jobs of the whole operation...

I want to move.

Remove the dive ladder.

NARRATOR: ...installing the foundations for the platform legs.

The platform must be built on rocks 100 feet underwater.

JIM CONROY: To be able to put the platforms at this level is quite a feat.

NARRATOR: Dive superintendent Yurij Bean leads the deep-water dive team.

He has 18 years' experience of industrial diving.

It looks good.

NARRATOR: But drilling into the tough granite is a formidable task.

Okay, stop there.

NARRATOR: The divers must level the rock with jackhammers so a floating rig can start drilling the six-foot diameter holes for the platform legs.

MAN: Okay, up on the diver, Up on the diver, he's heading back.

NARRATOR: Working 150 feet down makes the job incredibly dangerous.

Divers can't stay at these depths for longer than 50 minutes.

Look up.

NARRATOR: If they do, they could develop the bends, when nitrogen bubbles form in the bloodstream, damaging nerves and body tissue.

BEAN: For me, managing the divers' safety is the most important thing.

Safety is first.

NARRATOR: After each shift, the divers spend about 40 minutes decompressing in a special chamber to stop gas bubbles forming in their blood.

You okay?

Yep, not a problem, got it.

NARRATOR: Once the divers have prepared the seabed, the drill team gets to work.

They lower a massive six-foot diameter drill down a tube to the seabed.

As it bites through the rock, a pump sucks up the debris.

Filters remove the rock and clean the water so it can be pumped back into the sea.

Drilling the 21 45-foot-deep holes that they need takes eight months.

SLOANE: Granite is your hardest rock, more than double the strength of sandstone and limestone.

It's most probably the worst place you could choose.

NARRATOR: In April 2013, almost a year after salvage work began, the team lowers the largest platform section into position and fixes it to the foundations.

The platform is designed to support the ship once she finishes rolling.

The Concordia is balanced on two rocky outcrops, leaving the middle of the hull unsupported.

While the vessel is rotating, she could break in two.

To plug this gap, Nick has an ingenious plan.

First, divers will position huge fabric bags under the keel.

Then, they'll inject them with cement to build stacks of rock-hard mattresses.

This level bed of concrete should support the hull of the ship as they roll her onto the platform.

SLOANE: The finish of the cement bags is critical to the success of the parbuckling project.

Each one is sort of 40, 50 cubic meters, and it's just this massive wall 20 meters high.

It's like the Great Wall of China.

NARRATOR: Over the next ten months, the team will install 1,200 of the giant bags and pump them full with 20,000 tons of cement.

It's a huge operation, but on its own, it won't be enough to support the ship.

On the mainland in Milan, engineers are analyzing a unique survey of the crash site.

TULLIO BALESTRA: We can see that in principle, we can lower down this before it floating by four or five meters.

NARRATOR: Using sonar and lasers, surveyors have built a detailed 3-D visualization of the ridge that the vessel is clinging to.

BALESTRA: So if you have some other sections to show me.

NARRATOR: The images reveal that 290 feet of the bow hang over the edge of a cliff.

BALESTRA: It's been discovered that we could have significant deflection of the bow, and that could cause a problem during the refloating phase.

NARRATOR: To find out what will happen to the bow when they rotate the wreck, engineers create the world's largest supercomputer simulation of a ship.

It reveals a horrifying scenario.

As the vessel starts to roll onto the platform, the unsupported bow could sag or even snap off.

It's like a patient with a spinal injury.

So you're going to get a lot of twisting, and with the forces, you could lose the bow.

NARRATOR: It's impossible to extend the platform to support the bow.

The drop on the seabed is too steep.

We have to think of something new and something that has to be shaped according to the shape of the bow.

This is becoming critical.

So here we are.

NARRATOR: This is a major blow.

Without a plan to support the bow, the team can't raise the ship.

While the engineers go back to the drawing board, the operation to raise the Costa Concordia enters a new phase.

In Livorno, 90 miles from the wreck, workers are assembling the air tanks to install on the side of the ship.

These will play a crucial role in turning the ship upright.

The tanks, called sponsons, are huge, towering over 100 feet high.

Massive barges deliver each tank to Giglio.

Today's mission: attach the first tank onto the port side of the ship.

Crank up on the boom, up on the boom.

Up on the boom.

Okay, sounds good, perfect, thanks.

NARRATOR: The tank weighs 540 tons.

It's 11 stories high, but must be positioned within two inches of its neighbor.

SERGIO GIROTTO: It is a matter of precision.

To install with a millimeter precision, you can image how delicate it is.

NARRATOR: Once the giant tank is in place, welders fix it in position.

In the next four months, the team must attach ten more tanks to the port side to be ready to parbuckle the ship in the autumn.

The fine summer weather brings rapid progress and some good news.

The engineers have devised a plan to prevent the bow from falling off when they pull the ship upright.

They will build special air tanks, called blister tanks, that will cradle the bow.

To position them, mechanics will flood them with water.

When they refill the tanks with air, they'll form a huge, floating collar providing lift to support the bow.

With the parbuckling operation scheduled for September, building the tanks is a race against time.

It really wasn't until March that we decided that the blister tanks were the right solution for the problem, and so now we had to essentially, with just a couple of months left, we had to design, contract and get these things built and then get them installed.

NARRATOR: But they do it.

In August, a colossal vessel arrives in Giglio carrying the pair of giant blister tanks.

Altogether, they weigh 1,700 tons.

That's seven and a half times the weight of the Statue of Liberty.

GIROTTO: The blisters are as tall as a 15-story building.

To match the attachment on the bow with the precise inclination I think is something that has never been done, has never been attempted.

NARRATOR: To attach the blister tanks securely, the team must first remove the propellers of the bow thrusters and replace them with huge steel pins.

Only then will they be able to lock the blister tanks into place.

GIROTTO: The pull of the structure, it is 6,000 tons, so to move an element like this, it is quite a challenge.

NARRATOR: The team slowly floods the tanks with seawater to submerge them.

You want to run the big winch all the way back to the stern.

So it's a very tricky operation.

Normally in these kind of operations, you're lifting these type of weights out of the water, not putting them in the water.

NARRATOR: It takes six whole days to position the tanks.

But at last, they are in place.

The tanks should solve the bow problem, but at a price.

15 months after starting work, the cost of clearing up the wreck has now exceeded the half a billion dollars it took to build the vessel.

September 2013.

With the underwater support platform, concrete mattresses and air tanks all in place, the team is ready to attempt to rotate, or parbuckle, the vessel onto the underwater platform.

This is the critical maneuver they've been working towards for 20 months.

But have they thought of everything?

Are all their calculations correct?

You'll never be 100% ready.

And you say, "Are we as good as we can be in the time that we've been allowed?"

The trending forecast, that it's getting a little bit worse on Wednesday and Thursday, bothers me a bit.

NARRATOR: There are two big unknowns.

The first is the weather.

(thunder rumbling) Overnight, a storm strikes, threatening to shut the operation down... as the world waits for news.

REPORTER: This operation is going to be delayed for an hour.

That's because we had some very bad weather last night.

NARRATOR: The storm clouds clear, but the other big unknown remains: whether they have enough pulling power to wrench the ship off the reef.

All the power for rotating the ship will come from 36 hydraulic jacks attached to the tops of the air tanks.

Inside them, hydraulic teeth grip strands of cable and pull them through their jaws.

The jacks will work in unison, pulling on 36 cables anchored to the underwater platform.

The idea is, as the jacks pull the cables tight, they will wrench the ship up and off the rocky ridge.

That's the plan.

But in the 20 months since the ship capsized, she has become attached to the seabed.

SLOANE: Since she first settled on the rock, she's actually molded herself around the rock, and she's subsided by about three meters.

When you try and parbuckle her, there will be what they call a break-out force, and that's to tear her off the rock.

And that force is unknown.

NARRATOR: For Nick, it's the moment of truth.

SLOANE: You are nervous, but your mind is racing.

"What have we forgotten?"

You've been over the checklist many times before.

Some things you can control, some things you can't.

NARRATOR: The operation's nerve center is on a barge in front of the ship.

There's a risk the parbuckling could break the wreck apart, so Nick orders everyone off the vessel.

Just confirm all personnel off the Concordia.

NARRATOR: The operation gets underway just after 9:00 a.m.

Okay, we're going up ten percent.

NARRATOR: Computers control all 36 jacks.

SLOANE: We have almost 13,000 tons of pulling force on the offshore side, but everyone's nervous because we're not sure what the break-out force is.

NARRATOR: Even though the jacks have the capacity to pull with nearly 13,000 tons of force, the crew estimate that they will only need to apply 5,000 tons to dislodge the ship from the rocks.

That's still one and a half times the force of the space shuttle's rockets on take-off.

But as they reach the magic number of 5,000 tons, nothing happens.

Any movement?

MAN: It's a little bit heavy.

SLOANE: When we got to 5,000 tons, things went pretty quiet.

NARRATOR: The ship doesn't move.

They put more force on the cables.

Okay, let's try for 6,000 tons.

SLOANE: 6,500 tons, you get a bit nervous because you say, "Okay, now we're right at the upper threshold of where we should be."

NARRATOR: They keep increasing the force, and finally, something starts to happen.

SLOANE: And at 6,800, 6,900 tons, she started coming up.

NARRATOR: Finally, the giant vessel starts to break free of the rocks and rise from the sea.

Parts of the vessel, submerged for the last 20 months, emerge, covered in slime and rust.

The ship could break open at any moment, spewing toxic products into the sea.

So they surround it with oil booms to protect the beaches.

Spotters circle the ship, keeping an eagle eye out for pollution as she rises.

Slowly, the Concordia emerges from the depths in one piece.

It takes over seven hours to haul the ship one-sixth of the way up.

HABIB: We were about two hours late getting started, and it was going a bit slower because we're pulling a little more force than we originally intended to pull, so it's a little bit more force, it's a little bit slower.

NARRATOR: With the ship precariously balanced, they can't stop.

They have to continue.

Now the team must undertake the second challenging stage of the roll... in the dark.

The jacks may have pulled the wreck off the rocks, but there's a danger that gravity might crash the ship onto the platform.

The only things stopping this are the air tanks that act like giant water wings keeping the ship afloat.

Once they've caught the vessel, the team plans to slowly flood the tanks with water, hoping to carefully control the ship's descent onto the platform.

HABIB: 40 degrees is the point where gravity will take over, and so we will need to be very careful there.

That's where we start to transition from pulling to ballasting, or filling the tanks with water.

NARRATOR: As they lower the massive vessel inch by inch, six underwater robots scrutinize the hull to make sure she's rolling on target.

(applause) NARRATOR: At 4:00 a.m., the Costa Concordia touches down on the platform.

It's the first time the ship has been level in 20 months.

(applause) PORCELLACCHIA: It was a perfect operation, I would say.

And I have to say that there are no evidence so far of any impact to the environment.

NARRATOR: Although the wreck is upright, its hull still sits submerged about 100 feet below the water line.

The next day, Nick's anxious to inspect just how badly smashed the ship is.

All the work will be in vain if the ship is too badly damaged to refloat or tow to the scrapyard.

SLOANE: So we'll start off just between the starboard bow and the Pioneer.

NARRATOR: For the first time, the crew gets a good look at the wounded vessel.

You see that damage just underneath the blue crane.

She actually slid down the cliff three meters, and that's why all the balconies have been moved up.

Almost it looks as if the whole ship is bent.

The damage looks pretty bad, like a bad car crash.

NARRATOR: There are two massive indentations in the starboard side, evidence that the ship was resting on two subsea mounds of rock.

Underwater, there's another problem.

This is the bow side.

NARRATOR: A massive vertical crack in the hull has opened up.

MAN: As you can see, the crack is about 500 millimeters wide.

BALESTRA: And this opening is extending down.

We have discovered there was a crack starting from the bilge area.

Inside, there is some deformation of the decks.

NARRATOR: The 40-foot-long crack makes this brittle ship even more delicate.

If it widens and the vessel breaks apart, it may be impossible to tow her away.

Three months after the parbuckling, as December storms batter the vessel, the crew can only hope she is strong enough to survive her third winter on the rocks.

The weather's now more rain, more seas.

The temperature is dropping.

You can get three to four, five meter seas.

NARRATOR: They are close to completing the salvage operation, but now must wait for better weather.

Spring 2014.

The Costa Concordia has survived the winter.

With calmer seas in the Mediterranean, the salvage team can begin the final stage of the mission.

It's a race to remove the wreck before summer tourists arrive to soak up the sun.

To refloat the ship, they need to boost its buoyancy.

They'll fix 15 more tanks onto the ship's starboard side to match the tanks flanking its port side.

By slowly pumping air into the tanks, forcing the water out, they'll create a gigantic life jacket around the vessel with 66,000 tons of lifting force.

SLOANE: K4, K4, mobile one.

MAN: Go ahead.

Okay, if you can come onto the bow.

NARRATOR: A crane must lower each tank into place where divers will securely attach it to the ship.

SLOANE: Okay, she's all yours.

Can you stand by to come up on your whip line?

Standing by.

Down easy on the hook.

Coming up.

Swing easy to the right.

NARRATOR: Four giant chains and four wire ropes will hold the tank in place.

SLOANE: One more connection to make, and we'll have the fourth chain in by 9:00 this evening.

Okay, locked, check the other one.

MAN: Locked.

NARRATOR: It takes two months to install all the tanks.

But the achievement comes at a terrible price.

While working underwater, one of the divers is killed in a tragic accident.

It's a stark reminder that this is a dangerous job.

With the tanks installed, the team is now ready for the final stage of the operation: refloating the ship.

26 months after work began, the day finally arrives when they will attempt to raise the Costa Concordia.

The operation's nerve center has moved to the top deck of the ship.

SLOANE: VC, VC, mobile one.

MAN: Go ahead.

Yeah, okay, but what's the diver doing at the moment?

NARRATOR: This is a critical moment.

As Nick pumps air into the tanks and the ship begins to rise, water will rush out of submerged rooms and hallways.

SLOANE: You've got a lot of decks of water that's going to be trapped in the decks as we bring her up.

So we've got to do it one deck at a time and let that water flow out.

If you did it too quickly, then you'd lose stability and she'd most probably roll over.

NARRATOR: To prevent that catastrophe, they must raise the ship with extreme caution, inch by inch.

23, 65.

We're going to start 18 now.

NARRATOR: On Nick's signal, the crew fires up a bank of powerful compressors which start pumping air into the tanks.

It takes 11 tense hours to raise the ship seven feet up off the underwater platform.

HABIB: So deck number six has come out of the water.

It's tough to see from this side, but deck six is now out of the water.

How long we need...?

870.

NARRATOR: In controlled stages, they pump air into the tanks for nine days and nights, raising the ship 46 feet.

HABIB: Deck five will come out of the water, deck four will come out of the water, and then we hope deck three will come out of the water.

And the water level will be just below deck three, so that will leave five more decks underwater.

NARRATOR: Finally, the Concordia floats high enough for tugboats to come and tow her away.

PORCELLACCHIA: The bow came out of the water.

Now it looks like really a ship.

This is spectacular.

(applause) NARRATOR: 923 days after she capsized, and following an extraordinary engineering operation, the Costa Concordia sets sail on her final journey to a shipyard in Genoa, where she will be cut up to be recycled.

The total cost of salvaging the ship is now estimated to be $1.2 billion.

But no one can put a price on the human cost.

PORCELLACCHIA: Mixed feelings now.

This is not joyful as it should be, because we cannot forget that the origin of this is a tragedy.

NARRATOR: 32 people lost their lives in the original disaster and one during the salvage.

Everyone involved in raising the Costa Concordia can take pride in a great engineering achievement.

But it's a bittersweet triumph.

The harsh truth is all the effort, all the astronomical expense, were to clean up after a catastrophic accident that should never have happened.

They come from below... ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪