Off the coast of South Korea lies the island of Jeju, home to one of the most extraordinary traditions in the world.
For centuries, women known as Haenyeo—which means “women of the sea” in the Jeju language—have been diving without oxygen tanks to gather seafood.
Now, new research from the University of St Andrews shows that these women’s abilities rival, and in some cases surpass, those of diving mammals like sea otters and sea lions.
The study, published in Current Biology, tracked the diving behavior and physiology of seven Haenyeo, aged between 62 and 80, as they harvested sea urchins.
Using specialized instruments typically designed for studying marine mammals, scientists were able to measure heart rate, oxygen levels, and movement during their natural dives.
The results were astonishing: despite their age, these women spent 56% of their total diving time underwater during two to ten hours of daily diving. This is the highest proportion of time spent underwater recorded for any humans.
The Haenyeo’s skills are deeply tied to Jeju’s culture. Their short, quick language expressions are said to have evolved from the need to communicate rapidly at the water’s surface between dives.
Recognized by UNESCO as an Intangible Cultural Heritage, this practice represents not just survival, but also community, resilience, and a bond with the ocean.
What surprised scientists most was how differently the Haenyeo’s bodies responded compared to typical diving mammals.
Many animals show a “dive response,” where the heart slows down and blood flow shifts to protect vital organs.
But the Haenyeo displayed elevated heart rates and only mild oxygen drops in the brain and muscles. Researchers believe this unusual adaptation may be linked to their style of short, shallow, and frequent dives, which create unique demands on their bodies.
Dr. Chris McKnight, senior research fellow at the Scottish Oceans Institute, explained, “The Haenyeo are just incredible humans.
Their diving abilities are known to be exceptional, but being able to measure both their behavior and physiology while they go about their daily work is really unique. Comparing them to aquatic animals shows just how remarkable they are.”
The study also highlights the cultural and human dimension of this tradition.
Co-author Dr. Melissa Ilardo of the University of Utah recalled how the Haenyeo welcomed the research team into their daily routines, sharing food, stories, and laughter in their gathering places, called bulteok. “We feel incredibly lucky to partner with them,” she said.
Yet, this way of life may soon fade. Today, around 90% of Haenyeo divers are over the age of 60. As possibly the last generation continues their work beneath the waves, the study offers a rare and intimate glimpse into a vanishing tradition.
It is both a scientific marvel and a reminder of human resilience, endurance, and the cultural treasures that live—and sometimes disappear—beneath the sea.
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