Having heard from friends about the good trail running race in South Korea's Jeju Island, professional endurance athlete Jose Jeuland signed up for last year's edition.

Besides coming in fifth in the 50km Jeju trail running race, the full-time photographer came back with another prize - precious photographs of the haenyeo. The group of South Korean women dive as deep as 30m without heavy-duty breathing equipment - just a diving suit, lead-weighted vest and goggles - to catch seafood and collect seaweed to sell.

Jeuland, 35, a Frenchman based in Singapore, went back twice to photograph them in action. The trips snagged him an extensive collection of about 200 pictures, shot in black-and-white and colour.

He has put 12 of these on show at the East Garden Foyer of The Fullerton Hotel in an exhibition titled Haenyeo - Photography Exhibition by Jose Jeuland. It runs until Nov 23.

Those who like the images can purchase prints. Prices start at $3,500 for a 45cm by 30cm print and go up to $10,000 for a 225cm by 150cm print.

The pictures show the women at various stages of work. At different villages across the island, they meet and prepare for their day by downing energy drinks and slathering on sunscreen. Just before taking the plunge, they put on their masks. They are also shown post-dive, cleaning shellfish and drying seaweed.

Jeuland never planned on making a photo series about the women. Hoping to make the most of his time while at Jeju for the race, he researched online for interesting subjects to photograph there.

His search threw up an image of a woman in a diving suit. His interest piqued, he did more research and found more images.

"I had never heard of the haenyeo before that. I liked the pictures I found online because of their aesthetic. There were these old ladies in wetsuits... you don't see that often," says Jeuland, who is married to a Singaporean.

Gearing up for his first trip there, he downloaded a book about the haenyeo and found out it was only women who freedived. Seasoned sea veterans, they can hold their breath for two to three minutes as they scour the seabed for shellfish.

Nicknamed the Mermaids of Jeju, the community has shrunk over the years. A 2015 Financial Times article reported that there were more than 14,000 divers in the 1970s, but the number has since decreased to fewer than 4,500. Most of them are in their 60s or older.

While Jeuland was keen to photograph them, he did not have an easy start. Through social media, he contacted South Koreans who had photographed the women, but they discouraged him from seeking out the haenyeo.

He says: "They told me the women are not happy to be photographed. But I wanted the challenge, even though I didn't know how it would turn out. If it's too easy, there's no point anyway, as many people can do it."

When he reached Jeju, he armed himself with maps and went to villages where he knew the women live. Not speaking Korean did not hinder his efforts - he used sign language to tell the women he was going to photograph them and relied on South Korean tourists or his homestay owners to help him make signs they could read.

Some of the haenyeo found him amusing, especially when he followed a group out to sea without diving gear. They were impressed he could keep up as they swam 2km out to sea and managed to stay underwater for about a minute.

"They kept saying it was impossible and that I would go back to shore after swimming about 200m. To me it was nothing as I swim 4km to 6km in the pool as training.

"The women gave me more respect and accepted me into the group," Jeuland says. He has also photographed other fringe communities, such as the indigenous tribe of Sri Lankan Veddas and elderly people aged between 89 and 100 in Okinawa, Japan.

His first trip was a spontaneous photo shoot of the haenyeo. But for his second and third trips to Jeju, he took along diving gear and underwater camera equipment. He also deployed a drone to capture overhead shots.

The self-taught photographer, whose specialities are portrait and black-and-white photographs, hopes to return to shoot videos of them. He also hopes to publish a book next year with the remaining images.

"Even if it's not to photograph them, I would just love to watch them working," he says. "They are real athletes. Every day is an amazing performance in the water."