Shin Ho-jin had been freediving only a little over a year – gathering oysters, seashells and other marine life by hand – when she spotted the cluster of abalone. Eager to show the older, more experienced divers that she could keep up, the 37-year-old took a deep breath and was about to plunge toward her prize find when she heard a shout: “Ho-jin, don’t go there!”

It was the 69-year-old Lee Bok-soon, Shin’s boss and the captain of the boat. The experienced freediver of more than 50 years, often called Omma (Korean for mother) by her recruits, had seen that Shin was about to swim right into an old fishing net.

Getting caught in ocean trash is only one of the many trials faced by the haenyeo, the remarkable tribe of South Korean female freedivers who have made headlines in recent years as a supposed “dying breed” of elderly women – a recent survey by the North Gyeongsang provincial government found that more than more than half of the region’s divers were more than 70 years old (9.2% were aged 80 years or more) – preserving an ancient but soon-to-vanish tradition.

Lee herself, and other veteran haenyeo, thought the same, that they would be the last to pursue the centuries-old vocation on Geoje Island, off the south-eastern tip of the Korean peninsula. It is a place from where for years young women would leave to pursue more comfortable jobs.

Then, to their surprise, came the new recruits.

“Unlike other places, the number of young haenyeo has been increasing on the island in recent years,” said Soonam Ruy, a government official at Geoje City Hall.

The first haenyeo – or “women of the sea” – hailed not from Geoje but from Jeju, South Korea’s largest island, and eventually spread along the whole coast.

“During the Japanese occupation the haenyeo profession brought an entire paradigm shift to the lives of females in Jeju,” says Lee Seohyeon, a professor in journalism and public relations at Jeju National University. “Diving let them escape from the shadow of men and achieve a level of independence that few other women in Korean society had”.

It was initially a vocation born out of need, with many haenyeo continuing to work past retirement age. Many of the older women did not expect the practice to continue as South Korea’s economy diversified and the country grew more prosperous, but in 2016, when Unseco inscribed Jeju haenyeo on the intangible cultural heritage list, the country experienced a wave of enthusiasm for it.

It is not an easy line of work: there is less food to harvest these days, as well as looming environmental threats and injuries caused by water pressure. According to Son Moon-ho, a researcher at the National Institute of Fisheries Science, the climate emergency has heated the ocean, changing the habitats below. “Over the past 50 years, the surface water temperature in Korean waters has risen by about 1.5C, which is about 2.5 times higher than the global average,” he says. “Some fish species are changing and shifting their habitats.” Corals once teeming with life are now grey and lifeless. Large forests of seaweed have disappeared.

Despite there being less marine life to catch, haenyeo are determined to take care of the ocean – to live with it, not against it. If the shellfish they have caught are too small, they let them go. If the sea cucumbers are better to harvest the following year, they wait.