[music playing]
NARRATOR: And while sharks have always
been present along this massive shoreline, starting in 2010,
they become a problem.
More than 60 attacks in just 10 years,
triple the number of incidents from the preceding decade--
it's an unprecedented uptick.
Shark attacks in Western Australia previously were rare.
Now they're almost regular events.
NARRATOR: Not only that, the spike includes a horrifying 11
fatalities, earning this tourist haven a terrifying designation
as Australia's deadliest coast.
[dramatic music]
TREVOR WHYTE: The amount of vicious attacks--
there's no question.
It becomes talk of the town.
People are scared to go back in the water.
NARRATOR: With residents demanding action,
authorities put prevention measures
in place, including aerial surveillance
and beach enclosures.
But the attacks just keep coming.
So investigators take up the case in a bid
to stop the bloodshed and keep it from recurring elsewhere.
BLAKE CHAPMAN: The more we can research into what's happening,
then the more human fatalities and human trauma
we're going to be able to prevent.
NARRATOR: So what's causing the sharks of Western Australia
to suddenly go on a rampage?
Shark expert Johann Gustafson believes
that a crucial first step in solving this mystery
is to identify the culprit.
So he turns to a piece of evidence
from the attack on Elyse.
So here we have a fragment of tooth that
was lodged within the victim.
NARRATOR: Gustafson thinks this tooth must belong to one
of three species which are responsible for the majority
of the attacks worldwide.
The first is the tiger shark.
[dubstep music]
So here we have a tiger shark jaw.
And we see on one side of the jaw,
the blades are pointing to the left,
where on the opposite side of the jaw,
they're pointing in the opposite direction.
NARRATOR: This allows tigers to rip their prey
from both sides of their teeth as they shake
their heads back and forth.
A second likely culprit is the bull shark.
[dubstep music]
JOHANN GUSTAFSON: So with our bull shark,
we have here a completely different shape of tooth.
Quite pointed, serration is quite sharp.
NARRATOR: The bull shark's powerful pointed teeth
enable it to slice through its victim
in one quick lethal motion.
But Gustafson believes the shape of the tooth from Elyse's wound
indicates a different predator.
With this tooth fragment, it's perfectly triangular.
And it's quite serrated on both sides.
Without doubt, I can conclude this came from a white shark.
[electronic music]
NARRATOR: Great whites are the largest
predatory fish on the planet.
They use their powerful tails to propel them through the water
at upwards of 25 miles per hour, often
striking their prey from below.
But this identification isn't limited to Elyse's attacker.
Of the more than 60 attacks where the species is known,
the majority of culprits are white sharks.
So what's causing great whites here to act so strangely?
And could it be indicative of a behavioral shift
happening across the globe?
Perhaps the answer relates to a booming industry that's
centered around this iconic species,
one that occurs in several locations but all
began down under--
cage diving.
Shark expert Dr. Dan Huber explains.
The way cage diving operations work
is that boats use chum to try and attract sharks to the area.
People then get into cages, which are submerged
in the water, to get much, much closer to very dangerous sharks
than they would otherwise be able to.
NARRATOR: Cage diving has been a fixture of Australian tourism
for decades.
But around 2010, something changed.
DAN HUBER: In 2010, when the spike in shark attacks began,
the number of days that chumming occurred on the water
had doubled compared to the previous year.