[splash]
- Across the Whitsundays, hundreds of baited cameras
are deployed and listening stations fixed, as scientists
race to understand why these previously
safe waters have turned deadly.
And as the footage comes in, one big clue emerges--
the poor visibility.
- What we have here is a satellite
image of the actual water clarity
of the Whitsundays area.
It's showing the turbid waters versus the clearer waters.
And as you can see, most of the Whitsundays region
itself is quite turbid, including Syd Harbor in here.
You don't get the bluer waters till you move offshore.
These turbid waters are probably driven
by the actual sediments coming off the land
and out of these river systems.
Now, the interesting thing about these river systems
is that these are pretty key habitats for bull sharks.
- In the last 20 years, bull sharks
have been responsible for five attacks in Australian waters.
Armed with an incredible sense of smell
and a sixth sense that allows them to detect vibrations
in the water, they're perfectly adapted for hunting
in murky conditions.
But without vision, they can make mistakes.
- Most shark bites are cases of mistaken identity.
If you live in an environment where you can't see very well,
you have to be very, very quick and very decisive.
So they'll bite quickly and sort of ask questions later.
So this is consistent with at least
the first bite in Syd Harbor.
This is one bite that's removed a chunk of flesh in one
fell swoop.
If I was a betting person, I would lean towards this being
inflicted by a bull shark.
- On the Australian mainland, Richard and Adam's
colleague, Andrew Chin, is following
a different line of inquiry.
He's trying to discover why these previously safe waters
might have turned so deadly.
- And what we were looking for is the perceptions of people
who had been to the Whitsundays over the years to understand,
what sort of things had they seen?
What did they think was happening
in some of these different anchorages, like Syd Harbor?
Was there anything that people were doing that could explain
what might have just happened?
When we have a look at the data, it's obvious that Syd
Harbor is a very busy place.
There's a lot of people anchoring in there.
There's a lot of activities going in there.
People are paddleboarding.
People are swimming.
So you got a lot of waterborne activity.
You also have people discarding rubbish,
throwing food scraps over the side.
Some people are even fishing or baiting in these anchorages.
Those two activities don't go hand in hand.
Sharks are smart.
They will learn.
They're not going to waste energy swimming
around the whole ocean looking for food
when you can get it delivered to you off the side of a boat.
- Throwing food waste overboard is
illegal in Whitsunday waters.
But the team unearths evidence that the practice continues.
Could this be triggering the attacks?
- It definitely was a turning point.
You start putting two and two together of, like, hey,
these people are jumping off a boat
or falling off a paddle board and getting bit straight away.
And there's reports of lots of food going
in the water, lots of boats.
- If you imagine being a shark in that situation,
you're cruising around.
There's food scraps going in the water.
Smell can drift for long, long distances, as well.
So they could be following that up current to its source,
thinking, what's happening here?
As more scraps go in the water, then they
can feel the commotion of little bait fish
zipping around and going for a feed
and all that kind of stuff.
So there's a lot of stimulus in the water.
When they switch into feeding mode,
they're, like, a bit more on edge.
And they're, you know, like, oh, OK, where is this?
Where is this?
I'm trying to find the source, trying to find the source.
The visibility is bad.
Can't really see around.
There's a huge shadow above me.
But something's under it.
And then, splash.
Ooh, oh, cool.
I'mma go for it.
And unfortunately if it's a person that's
jumped in at that stage, they will come
through at high speed and bite.
- The possibility that human activity
could trigger the attacks is new and alarming.
It has implications for every bay around the world where
boats gather in large numbers, particularly
locations in Southern Florida.
- The other thing that a boat does
is it provides you with a hiding spot, right?
So you have this big thing of shade that hangs over you.
It's structure.
It's kind of like a movable ambush point for a shark.
And it's interesting that many of the shark bite
accounts that we have, not just in Syd Harbor
but everywhere, people have been bitten when
they've jumped into the water.
The splash, and then they've been struck.
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