The first images of the new Netflix/A24 documentary “The Deepest Breath” are disturbing: A free diver is pulled from below the ocean surface by safety divers. They rip off her mask. Her eyes are rolled upward and she is unresponsive. Working feverishly, the safety crew resuscitates her.

And this is … normal?

Indeed, it is. Minutes later, the free diver, Italy’s Alessia Zecchini, is back in the water.

The psychological makeup of an extreme sports athlete is fascinating. There’s a drive for thrill-seeking that is understandable, even admirable, but only to a point. When does thrill-seeking cross into insanity?

Some extreme sports seem relatively sane. Surfing and auto racing can be dangerous, but loss of life is rare (though it does happen, and there is clearly risk).

Watching “The Deepest Breath,” I was reminded ofAlex Honnold, the person who climbed Yosemite’s El Capitan without the aid of ropes or other equipment in the 2018 documentary “Free Solo.” Like free soloing, free diving, in which divers go as deep as a 30-story building in one breath, seems designed to ultimately kill you.

“The Deepest Breath” focuses on Zecchini, a world champion who was 25 at the time of filming in 2017, and Irish free diver Stephen Keenan, a 39-year-old who retired from competition to become a trainer and a safety diver. From the beginning of Laura McGann’s documentary, there is a feeling of dread. You know something bad is going to happen.

The fathers of Zecchini, whose quest is to beat the women’s record free dive of 100 meters, and Keenan seem sad as they discuss their children. Other friends recall key moments in the two athletes’ professional lives. All of this is juxtaposed with scenes of sun-dappled joy as we are introduced to the insular world of free diving, a tight-knit world not unlike the “submersibles community” that many became aware of in the wake of the recent OceanGate tragedy near the wreck of the Titanic.

There are breathtaking underwater photography and exotic locales from the Bahamas to Dahab, Egypt, to take in as we get to know Zecchini and Keenan. The former was born and raised in Rome and wanted to become a free diver since before she was a teenager; the latter was a drifter who traveled extensively in Africa in search of adventure, finally finding his calling beneath the waves.

McGann, whose 2016 documentary “Revolutions” explored the women’s roller derby scene in Ireland, spins a compelling yarn about two fascinating people, although she doesn’t go much below the surface. What, for example, is Zecchini like out of the ocean? Does she do crosswords, or have any kind of other hobby? Does she have goals once she’s done with free diving?

Without specifically giving anything away, there is a downer element to “The Deepest Breath,” but also an uplifting one. In general, however, it’s hard to call any free diver’s death a tragedy. This is the dangerous life they chose, and each one would say they’d rather live a short, exciting life than a much longer life of drudgery and boredom. Who am I to say it’s wrong?

Reach G. Allen Johnson:ajohnson@sfchronicle.com; Twitter:@BRFilmsAllen