in the shallows in greater numbers,

then it's not because of deep blue.

The reason for the attacks remains elusive.

But while scouring the ocean for an explanation,

experts come across something else

that also ensnares large amounts of a tiger shark's prey.

But it's not another sea creature.

In fact, it walks on two legs.

NAIA RAE FOX: I think the reason why we are having more sharks

here actually is because the amount of fishing

that's been going on.

NARRATOR: This is one of the island's most popular

activities, sport fishing.

Every year, recreational anglers haul in more

than 2 million pounds of fish.

That means that on any given day off the big island,

there are hundreds of fish being caught and reeled in.

And for scientists like Dr. Dan Huber,

these hooked sea creatures may be attracting sharks.

DAN HUBLER: A struggling fish, as its body

is twitching a bit, that motion is giving

off low frequency sounds.

And shark hearing happens to be tuned

into low frequency sounds.

This is definitely something that could attract a number

of sharks to the same area.

NARRATOR: So could sport fishing be drawing tiger sharks

into the shallows, thereby increasing

the risk of an accidental run in with people?

According to fisherman Rick Rieger,

it comes down to where the best sport fishing takes place.

To demonstrate, he heads out to an area well

known for the popular pastime.

RICK RIEGER: So this is our bottom here.

We have some of the steepest drop offs

in the whole world right here.

This is where you're going to see your tuna, your mahi-mahi,

your ono, your marlin.

NARRATOR: This location could hold a vital clue

to solving the mystery.

Called the pelagic zone, this open water

abyss extends thousands of miles between

the continental shelves.

It's home to an array of large sea creatures--

whales, manta rays, big game fish, and some of the most

dangerous sharks on earth.