JOHN YANG: Imagine scuba diving without a breathing apparatus, diving down hundreds of feet on a single breath and holding it for as long as three minutes.

That's freediving and extreme sport that's growing in popularity and interest.

The risks are high, some freediving sponsor considered as deadly as Mount Everest.

A documentary called The Deepest Breath is now streaming on Netflix.

It goes inside the sport following two freedivers, Alessia Zecchini and Steven Keenan.

It is both mesmerizing and terrifying to watch.

Earlier I spoke with Laura McGann the film's director, I asked her what drew her to the project.

LAURA MCGANN, Director, "The Deepest Breath": I read about Steven and Alessia in 2017.

And, and initially, I didn't know what freediving was.

So I had to Google what is freediving.

And I was mapped by these incredible images of people swimming underwater, almost like a seal or a dolphin.

Like with a seemingly without the urge to breathe.

I couldn't believe it.

Like I couldn't believe that this was something that people could do, that humans were capable of.

But then over time, as I learned more about Steven and Alessia, that's when the story, the gravity of the story and how universal it was, you know, it really just inspired me it made me feel like God, am I living my life to the fullest?

You know.

JOHN YANG: You're talking about how you it's hard to imagine people doing this.

We've got a clip from the film that shows Alessia freediving, and she's talking about the experience.

ALESSIA ZECCHINI, Freediver: After 30 meters, the pressure pushing me down.

It's called a freefall.

And this is, for me, the best part.

it feel like you're flying.

The silence, it's unique.

It's like being in the least quiet place on the earth.

JOHN YANG: The way she was talking about that, it's almost like a spiritual experience.

LAURA MCGANN: Absolutely, yeah.

Freediver say that you meet yourself down there, you know, you're holding your breath, there's nothing other than, you know, the ocean around you.

Anything that you might be kind of like, being not quite honest with yourself about in your own mind, you're going to find that there.

So it's like a deep meditation, you know, maybe in a similar way to like running a marathon and you know, you learn a lot about yourself when you're running marathon.

And like this it's such a kind of massive experience for the body that you do learn what you're capable of and what comes up for you.

I imagine I could and this is what I've heard.

JOHN YANG: You talk about when you're learning from your body.

We've learned recently what the pressures of deep ocean can do with the submersible that was going down to the Titanic.

Now these free divers don't go nearly as deep but there still is a fair amount of pressure that the water is exerting on them.

What did you learn about what that pressure can do to the human body?

LAURA MCGANN: You know, if you drop your goggles at the end at the bottom of the pool, okay, you've got a kick quite hard to get down there to get the goggles.

So it's the same in the sea.

So the first few meters, you've got to really kick quite hard.

But once you get to 10 and 20, then 30, the pressure above you then starts to push you down.

So you don't have to kick really hard to go down further.

But then what happens is when you turn around, come back up, you've got to work against that pressure.

It's like swimming against the current.

JOHN YANG: And they talked about something called lung squeezing, or a lung squeeze.

What's that?

LAURA MCGANN: So when you're going down another thing that pressure does -- pressure on your lungs, if your lungs actually do shrink to the size of a tennis ball, and then tissue in your lungs tears, and that puts blood into your lungs, and over time, if that is repeated, it creates like a scar tissue on your lungs and then it means your lungs can't absorb as much oxygen as they could have if you didn't have it.

So it can be quite, quite a dangerous thing to do continually.

JOHN YANG: So we're talking about Alessia Zecchini, and in the film, there's a clip of her winning her first open water free diving competition, which is only a teenager.

ALESSIA ZECCHINI: And I said, Let's see how deep I can go.

By holding your breath, you get to understand a lot of more about yourself.

I managed to descend to 52 meters.

JOHN YANG: That's Alessia Zecchini.

You tell the story of about freediving through her and through another diver Steven Keenan, tell us more about them.

LAURA MCGANN So Alessia wanted to be a free diver from the age of about 13, which was unusual, even in Rome, where they do pool free diving quite a bit.

And she wasn't allowed to compete really until she was 18.

Because she kind of turned up and was blowing everybody out of the water.

So the Federation really quickly brought in rules to say, you can't do this.

So she had to wait.

When she came back at 18, she had a lot of fire in her belly.

And she absolutely arrived like a rocket.

Steven Keenan, and on the other hand, is an Irish guy.

And he finished school and didn't really know what to do with his life.

He was a big fan of David Attenborough.

So he kind of went off to be, you know, his own version of David Attenborough explore the world a little bit and just really experienced what was out there.

And so the story is of how Steven and Alessia push themselves out into the world, follow their kind of gut instincts, and eventually come together.

And then what happens when they when they do.

JOHN YANG: This film really makes clear the hard work that these athletes go through to achieve their goals, and push themselves to achieve their goals.

But you also hear the great love they have for this sport.

What did you learn about their relationship with -- the diver's relationship with the sport with free diving?

LAURA MCGANN: One of the things that really struck me was that with the safety divers, you know, you have an athlete and a safety diver say at a competition or, you know, maybe even just a recreational dive.

And the agreement is whether it's spoken or not is that the athlete, if anything happens to me, while I'm down there, you, my safety diver are going to bring me back up to air, land, my family, you know, my life, that's where my life is.

It's up there.

It's not down here.

And that's the trust that like the ultimate trust exercise.

A safety diver could save a number of lives in one day, so build up this like beautiful kind of trust and bond in the community that I just kind of felt was really, really unique.

JOHN YANG: What do you want viewers to take away after watching this movie?

LAURA MCGANN: I'd love for people to get a sense of like, you know, life is short.

We're all passing through and how do you want to spend your time here.

I was struck by Steven's attitude to life and how he -- and his bravery by going out there alone into places that were unknown to him.

He said that he was going to, you know, go out and drink up every last drop of the earth and I just thought that is beautiful.

And so that's something that I really try and kind of take a beat every so often and just kind of think about where I am and just trying to connect with the moment.

JOHN YANG: A good thought.

The film is The Deepest Breath.

It's now streaming on Netflix.

The director is Laura McGann.

Thank you very much Laura.

LAURA MCGANN: Thanks, John.