- [Narrator] It's springtime off the coast of North Carolina and the OCEARCH team is trying to solve one of the great mysteries of the great white sharks, where they mate.

- We're talking about an ancient secret, right?

This is a 400 million year old secret that the ocean is deciding whether or not it wants to reveal to us or not.

- [Narrator] It's a daunting task in the face of North Carolina's turbulent seas.

- This time of year, in this area, when these big mature animals are here, the weather's tough.

It's super dynamic.

You got the Gulf stream colliding with Hatteras just north of us.

It's windy and maybe you're able to work one in four days across a 22 to 25 day trip.

And then you have to catch the right shark.

This isn't just a test, a test of endurance, a test of tenacity, a test of stamina.

If it was easy, it have been done right now.

- [Narrator] Since 2012, OCEARCH has tagged 84 sharks and mapped their range across the world using a gentle catch and release method that leaves the animal unharmed and outfitted with a tracker.

Discovering where their nurseries are, where they feed and forage.

And this is the last piece of the puzzle.

The team suspects that sharks are mating off the coast of North Carolina because they've seen adults converging here.

- And then all of a sudden the males just continue their sort of dumb male thing of going back and forth.

But then the females, all of a sudden shoot offshore from here and they make these enormous loops out into the open ocean.

I mean, way past Bermuda, all the way out to what's called the Mid-Atlantic Ridge.

Why would they do that?

And why just the mature adult females?

Well, we think that the best explanation is that's when they're pregnant and they're getting away from the rest of the population, getting away from any more harassment by males.

- [Narrator] Knowing where great white sharks mate is important.

- So if we can understand the entire life of a white shark which might run 80 years from birth to old age and death, then we can know where those critical places are in each step of the way.

So these animals have been severely depleted over the last three or four decades, and now they're making a return and our work is laying out a path for that return to abundance.

And also showing us where the critical habitats are where these animals face threats that we need to take into consideration.

- [Narrator] In the more than a hundred shark centered movies produced since JAWS, 97% of them featured sharks threatening humans and the antagonist in most of the films have been great white sharks.

Despite our anxiety around sharks, they have more to fear from us than we have from them.

Overfishing and bycatch, or getting caught accidentally in fishing nets, are the biggest threats to great white sharks globally.

And we're discovering that their presence in the ocean is crucial.

- And what we see when we lose our large sharks is we see the entire food web collapse.

Things like seals and squid and other things that sharks really keep under control begin to wipe out all our fry, all our baby fish and the seals will wipe out all the stripers, all the cod, all the red fish.

And so with sharks and our large sharks at such low levels we were in a situation where if we don't find out how to bring them back, how to manage them back, we were gonna really struggle to deliver a working abundant ocean to the future.

And that's why the white shark, things within their life history that are hugely important to make sure they return because they have a lot of challenges, right?

These animals aren't sexually mature until they're 20.

So they have to live 20 years just to replace themselves.

- [Narrator] And that's why OCEARCH has crossed the globe tracking great white sharks, revealing the secrets of how and where they spend their lives.

It's not just OCEARCH scientists that use this data.

At least 45 scientists rely on samples from OCEARCH's team to conduct critical shark research.

- We have to touch far less sharks than if all those 45 scientists were to go out and working on the white shark, for example and have to collect the sample size they need.

It would be potentially 45 times bigger sample size.

So it's a beautiful thing.

- [Narrator] The team found two males with elevated sperm counts off the coast of North Carolina, but they want a larger sample size to confirm this last life cycle mystery.

So they'll be back to brave the North Carolina weather.

- Now we're really ocean people.

And we were trying to get involved with things that help make sure our kids could go out and see if an ocean full of fish.

Our mission is to return our world's oceans to abundance.

It just happens that one of the primary paths to abundance happens to go through the white shark our apex predator and the balance keeper.