- [Narrator] Just when you thought it was safe to go back in the water.

- It's not that little.

- [Narrator] Comes a pointed reminder that you might wanna think twice, at least in Cape Cod.

- I guess the headline is there are lots of sharks here, more than we thought.

- Yes.

- [Narrator] Megan Winton of the Atlantic White Shark Conservancy is one of the authors of a new study documenting a surge in the population of great white sharks here in recent years.

- And what's your best estimate?

- So the best estimate is over that four year period that 800 individual white sharks visited the waters off of Cape Cod, which makes it among the larger white shark aggregation sites worldwide.

- She and her colleagues have spent years patrolling these waters tracking every shark they encounter.

- Nauset ORV, yeah.

- Has he got a tag?

- They recently let us tag along.

- We did just get one.

Okay, so it says, white sharks spotted a hundred yards off Southern most part of Nauset ORV.

So that's them.

Yeah.

Yeah.

So one of the eco tour boats just spotted a white shark a little bit to the north of us.

- Aha.

- So we're sending the pilot up to investigate and we'll see.

- [Narrator] Overhead they have a spotter plane.

The pilot Wayne keeps a sharp eye out.

- [Wayne] I think I just passed one.

I'm making a 180 here.

- [Narrator] On the boat they have underwater cameras and microphones and a ready supply of these things.

- It's just kind of like an easy pass for sharks.

This thing, I mean, that's the simplest way to explain it.

- Do you charge toll?

- We should start.

- [Narrator] A radio beacon with batteries that last 10 years.

Every time a tagged shark swims past one of these yellow buoys, it sends out a ping.

The conservancy relies on citizen sightings too from a growing number of eco tour boats.

- You get to see some?

- Yeah.

We saw one super shallow here.

About 14 feet, it wasn't tagged.

- [Narrator] The people on that boat tell us they saw a 14 footer here moments ago.

Every sighting from people or pings gets relayed to an app you can download.

Sharktivity, they've identified more than 600 individual sharks here over the past 10 years.

Many of the sharks are return customers, just like the beach goers.

- So I bet your app is fairly popular among beach goers.

- I mean, I'd like to think so.

It's been downloaded over a hundred thousand times at this point, and it's a great platform for us to report sightings when we're out on the water for eco tour boats to report sightings and for anybody who's out.

So it's a great citizen science tool.

It'll be more fun when there's a shark.

- Meagan and her team deploy a hydrophone, an underwater microphone, listening for a ping from a tracker.

- Oh look at wow.

- [Narrator] False alarm, all we find here is this school of stripers.

The shark apparently long gone.

It may come as a surprise to know that nearly 50 years ago when Steven Spielberg scared the pants off just about everybody with his iconic movie about sharks and this part of the Atlantic, the population of great whites here was in danger of dying out.

- We gotta get a bigger boat.

- [Narrator] Did Steven Spielberg help or hinder your work?

- Well, for me, Spielberg, you know, kind of motivated me to be a scientist, you know?

- Oh really?

- Yeah, yeah.

- [Narrator] You're here because of "Jaws"?

- I am, in essence.

- Greg Skomal was still in grade school when "Jaws" came out.

The movie caught his imagination in the best possible way.

- I was motivated by the scientist in the film, as were a lot of colleagues of mine at the time to become shark biologists, you know?

So as a young kid watching that, I was thinking, "Wow, this is a really cool job."

- [Narrator] Skomal has personally tagged more than 300 sharks.

Fulfilling his dream at a time when Cape Cod is finally beginning to see the dividends of decades of marine conservation efforts.

Over the last 50 years the Marine Mammal Protection Act gradually helped the seal population to rebound.

25 years ago, sharks were listed as a protected species too.

Now both species are catching up.

- If you think about it, in the time that both sharks and seals were gone, Cape Cod has exploded as an area that draws people to enjoy this environment.

And so now the predators coming back to feed on its prey, but it's overlapping with human activities.

And certainly humans are not used to that.

And so, but they're coming to grips with it.

- [Narrator] The team deploys a drone for a bird's eye view of the water.

What they tend to find is that the sharks spend about half their time in water that's less than 15 feet deep.

- We've got the seals which love the beautiful beaches of Cape Cod.

So do people.

And the sharks are coming in close to shore to hunt for seals.

So there is an overlap of these three species.

- Somebody who loves the ocean, loves the environment.

Many people do, they wanna see healthy shark populations, but they also might wanna boogie board and go surfing and get their swimming in.

And they're gonna have to change their behavior because of the presence of these animals.

- [Narrator] This morning, a shiver of more than 50 sharks spotted off the New York Coast.

On New York's Long Island, that's become an urgent issue over the past two summers there's been a series of shark attacks.

- [Greg] It has a tag.

- [Narrator] Finally, late in the day, a bonafide sighting.

- Pretty.

- [Narrator] Greg Skomal climbs out onto the pulpit like a friendly Captain Ahab armed not with a harpoon, but a GoPro camera, a 14 footer a teenager not yet fully grown.

Great white sharks are four feet long when they're born.

They can grow up to 20 feet long, their lifespan more than 70 years.

- So that shark right there is one that we tagged a few weeks ago, you know, right in this exact same area.

So clearly it's been sticking around.

And I think the only reason they stick around is if they're successfully feeding, because no point in staying in an area where you're not having any success.

I love he's just staying in the shallows.

- [Narrator] Most of the regulars have nicknames.

Not this one yet.

- Who gets to name it.

- We've got a donor in the queue who gets to name that shark.

And that program helps us fund the cost of research trips.

- So you contribute a little to the work that you guys are doing.

- Yes.

Yes.

- And you get to name a shark?

- Exactly, it's a pretty cool thing.

- How much does the Shark's name go for these days?

- $2,500, which covers the cost of a research trip.

- [Narrator] That nickname, will pay for another day out on the water like this one, adopt a Shark.

- It's basically an Adopt a Shark program.

(calm music)