What Shark Attacked?

There are over 500 different species of sharks,

each with their own signature predatory style.

But as sharks stalk the seas in search of their next meal,

encounters with humans become inevitable.

Oh, my God!

And in these rare moments captured on camera...

Oh, my God!

- -

There's blood everywhere.

...the chaos and confusion

has led to more questions than answers.

Now, a team of shark investigators will examine

the most intense viral shark encounters on the internet.

Wow, wow, wow. OK.

Oh, my gosh.

If that was a bull shark,

the outcome would have been fatal.

Analyzing the footage and aftermath of the attacks...

You get the entire jaw shape in his bite.

The shark that's in these videos,

that's actually a bull shark.

...to determine...

"What Shark Attacked?"

Sharks have evolved for millions of years

to become nature's perfect predators.

And when they identify potential prey,

they strike in an instant.

Shark!

Now, a team of Shark Week experts

will dissect the evidence of unsolved attack cases...

Oh, wow.

...to reveal the sharks responsible.

Sharks hit fast, hit hard, and get out of there.

So it's difficult to tell what kind of shark it was.

Brave kid.

Off the remote island of Ahe...

spear fisherman Josh Humbert

is heading out to search for mahi-mahi.

French Polynesia is essentially shark paradise.

You have everything from massive drop-offs,

you have atolls with passes, you have deepwater trenches.

I have been in that area, so I know how sharky it is.

It's in the early morning when Josh descends

upon a coral reef teeming with food.

He releases his spear,

securing his meal.

But as he turns to put it in his bag...

...he is ambushed by a large shark,

severing his leg...

leaving him to bleed out.

But Josh scrambles to the surface.

And is airlifted to a nearby trauma unit.

His leg is mangled, requiring two dozen stitches

to close the wound.

So what shark attacked?

So straight away, you have got the prey

for a variety of different sharks.

We can see in the video that we've got a lot of different

reef fish all schooling together.

Different sharks absolutely target different food sources.

If there was a turtle in the shot versus a fish,

I would say that's a great environment for a tiger shark.

But these are reef fish.

So watching the shark, there were a few things

that are really clear about its hunting style.

So you have an aggressive, fast-hitting shark,

and one that is rather territorial.

The behavior we see here is classic

of an opportunistic reef shark.

It's got the right body shape, the right coloration,

and without sounding stupid, it's on a reef.

But there are many, many different

reef shark species.

This could absolutely be a gray reef shark,

a blacktip reef shark.

It could also be a silvertip.

The reef sharks all kind of conform

to a very similar pattern.

That body shape, that mouth, the coloration,

everything works for the reef environments.

But the bite can really tell you

exactly what species did what.

Josh had a pretty solid bite on his leg.

And you get the entire jaw shape.

With the spacing between the teeth,

you can tell that the teeth are designed

for a shark that predates mostly on fish.

The triangular bite we're seeing here and the spacing

between the teeth is commonly what we see between

gray reef sharks and blacktip reef sharks.

What I didn't see is that very characteristic

black marking on the dorsal fin.

I think that with all the evidence

in the Josh Humbert case, that was a gray reef shark.

So when you're using a pole spear in really sharky areas,

the moment you hit a fish and those vibrations go out

into the water, the sharks can feel that,

and for them it is dinner's on.

They can be on you in seconds.

So if you have a shark obviously swimming away,

you have to even be careful if you're taking a fish

off your spear, because it can turn on you on a dime.

Luckily for Josh Humbert, he made it out with only

a series of scars and one hell of a story.

But 300 miles off the coast of Brazil,

Tayane Dalazen was not nearly as lucky

as she was freediving

off the coast of Fernando de Noronha.

The video of the incident shows her taking a deep breath-hold

as she explores the rocky bottom.

As she surfaces for air...

she is surrounded by a group of sharks

looking for food near the boat.

When suddenly...

her leg is snatched by a seven-foot shark,

dragging Tayane to the bottom of the ocean.

As she is running out of air...

the shark releases,

and Tayane fights to get to the back of the boat.

The shark leaves a curious circular bite mark behind,

leaving doctors puzzled.

So, what shark attacked?

In the video, there are both nurse sharks and lemon sharks.

Right before the bite happens, you actually see a shark turn

into frame and you see its face.

And what it has is it has the very characteristic

little barbells there. They're almost like a catfish.

And that is super, super indicative

of a nurse shark.

Shortly after the incident, Tayane released a video

on social media describing the bite.

The shark bit down and held his jaw on my leg

for several seconds. It had no suction.

The pain was very strong.

What Tay is describing points directly to a nurse shark.

While these guys are mostly known as suction feeders,

they also have an incredible grip with their jaw.

Nurse sharks do have an incredibly powerful

vacuum-like suction.

They also have a very vise-like grip

with backward shaped teeth that are hooked.

So, you can actually create

a lot of damage without the suction.

While nurse sharks are suction feeders, their jaws act like

a vise grip, clamping down on shellfish to crush its catch

and extract the meat.

People think that nurse sharks are really sweet and docile,

but any animal can bite,

and you are potentially going to have a very serious injury.

So, my question would be, just how much pressure

is a nurse shark capable of to really determine

how lucky Tay was in that situation.

So to determine this, Liz Parkinson is actually gonna

run a bite-force test on a nurse shark out in Bimini.

In order to test the true force of a nurse shark bite,

the team has contacted shark conservationist Liz Parkinson

to administer a field test off the coast of Bimini,

where the native nurse sharks

can reach over 14 feet in length.

One of the misconceptions that we hear all the time is that

nurse sharks are suction feeders

and they do not bite.

So, we're gonna dispel this myth and show everyone

just how powerful they can be.

We're gonna use this bite-force meter.

We're gonna try and get the shark to bite onto it

and then you can get the reading of that pressure.

At the end of the pole is a pressure plate

that will record the force of the nurse shark

as it clamps down on the fish head...

giving the team a measurement of the power behind the attack.

OK, you guys ready?

The area around the dock is surrounded by dozens of sharks

looking for an easy meal.

So this is kind of tricky.

We have a ton of bull sharks in here right now.

Just trying to get the bull sharks out of the way.

Bull sharks in this area can reach over 8 feet long

and are known to literally bully their way

to outfeed nurse sharks.

OK, here comes one in here.

If we can time this right, maybe...

Hold on.

There's a whole school of them coming in here.

Come on, girls, over here.

Oh, no, oh, oh, oh, come on.

Whoa, whoa, oh.

Oh, she almost got it. Let's try that again.

Let's see if we can get this.

This one. Here we go, guys.

Latches on.

No. No, she's missed.

Come on, baby. Come on -- oh.

What? Here we go, we got it.

What a fight.

The six-foot nurse shark latches onto the plate,

and the camera gives an inside look into its mouth,

showing the rows of inverted teeth

used to clamp down on their prey.

Back in California, Kinga is able to analyze the data.