Just over 1,000 miles off the coast of Australia lies New Caledonia, an island archipelago where the waters teem with life. This French territory, in the heart of the Coral Sea, is home to more than 9,300 marine species, including dugongs, manta rays and venomous sea snakes.

Among them is the greater sea snake, which can reach nearly 5 feet long and is more than capable of killing a human with a single bite. But such a fearsome capability doesn’t bother Monique Zannier, 75, one of a group of seven women, ages 60-75, who snorkel regularly in Baie des Citrons, a bay in New Caledonia’s capital, Noumea.

“The Baie des Citrons is our playground,” she said. “We are in it almost daily, and we know all its nooks.”

What started as good regular exercise for Zannier has turned into a bounty of data and information for scientists studying the aquatic snakes. Researchers seeking new insights into the ecology of these reptiles have come to rely on the women, nicknamed the “fantastic grandmothers,” to help keep track of the hundreds of greater sea snakes that visit Noumea’s shallow- water bays.

An article published in October in the journal Ecosphere highlights the fruits of this collaboration between the team of snorkeling scientists and the study’s lead authors, Claire Goiran, a marine biologist at the University of New Caledonia, and Rick Shine, an evolutionary biologist at Australia’s Macquarie University.

“The grandmothers should be congratulated,” said Harold Heatwole, professor of zoology at the University of New England in Australia who was not involved in the study. “They’ve made a great contribution to science.”

Their diligent data collection, he said, has resulted in more detailed information on the ecology of greater sea snakes than is available for any other wide-ranging sea snake worldwide.

Unlike their terrestrial cousins, sea snakes are largely understudied. Most sea snakes live far offshore and are dangerous to handle, so few scientists have the means or desire to study them.

“We know very little about sea snakes,” Shine said. “Almost everything we know about them comes from ones that were accidentally caught in fishing nets.”

In 2013, Shine and Goiran set out to learn what they could about the mysterious greater sea snake. They chose the Baie des Citrons as the venue for this study, despite greater sea snakes having been seen there only six times in the past eight years. Greater sea snakes have distinctive markings on their tails, so individuals can be easily identified from photographs.

With limited time to survey the bay and no full-time volunteers to assist them, Goiran and Shine got off to a slow start. During the first three years of the study, the pair managed to catalog only 45 greater sea snakes.

But that all changed in June 2017 when Goiran met Aline Guemas, a 61-year-old retiree. One morning, while Goiran was snorkeling, she saw Guemas photographing the reef with her camera.

“We started chatting in the water, and I explained to her what I was doing and she told me she wanted to help,” Goiran said.

Guemas started joining Goiran on her weekly surveys, photographing sea snakes and recording their location on the reef.

“I was very happy,” Goiran said. “She did exactly what I needed her to do.”

She encouraged Guemas to recruit other retirees, and before long she had assembled a team of seven.

“She told a friend and that friend asked another friend,” Goiran said. “It really came together by chance.”

Among the first to join the group was Zannier, who had taken up snorkeling as a form of physical therapy, as well as Sylvie Hebert, a 62-year-old retired nurse who has circumnavigated the globe by sailboat, and Marilyn Sarocchi, a 63-year-old gymnast with a fear of snakes.

“We meet every morning between 8 a.m. and 8:30 a.m. We wear our diving equipment, and we swim for one hour or two. Sometimes in summer we can swim for three hours,” Sarocchi said. “Back on the beach we have tea and enjoy the beauty of the site. It is very relaxing.”

Since the group’s inception, the “fantastic grandmothers” have conducted hundreds of snorkel surveys in the Baie des Citrons and identified hundreds of greater sea snakes.

“As soon as the grandmothers set to work, we realized that we had massively underestimated the abundance of greater sea snakes in the bay,” Goiran wrote in the study.

Photographs taken by the grandmothers demonstrated that within a 25-month period, at least 140 greater sea snakes visited the Baie des Citrons.

The research suggested that greater sea snakes might play a larger role in the functioning of their ecosystem than previously thought.

The grandmothers say they have been able to find so many more snakes because, as retirees, they have more free time for the search than the researchers do.

However, Shine insisted the grandmothers bring more to the table than just their free time.

“They understand what we’re trying to achieve, and they put enormous effort into helping us achieve it. ” he said.

Goiran agreed.

“They don’t take risks, and when you work with sea snakes, you don’t want anybody to take risks,” Goiran said.

The relationship between the grandmothers and the researchers seems to be mutually beneficial.

“We are very grateful to the scientists who let us have a part of their research,” said Genevieve Briancon, a 75-year-old retiree who joined the group shortly after its inception. “It’s very exciting. We learn a lot about sea life, and we are happy that our passion can be useful.”

For several members it has also helped them overcome a phobia.

Sarocchi added, “Before I started this adventure, I was very afraid of snakes. Now I no longer have any apprehension.”

Given that the bay in Noumea is occupied every day by hordes of local residents and cruise ship passengers, the larger-than-expected number of snakes serves as “a testament to the benevolent disposition of these snakes,” Goiran wrote in the study.

She hopes the data collected by her and the “fantastic grandmothers” will help conservationists improve protections for sea snakes. “The sea snakes in Noumea are doing fine, but in other places, sea snakes are endangered. We need people to realize that they are important so we can protect them.”

Of the 60 or so sea snake species across the globe, only two are considered critically endangered by the International Union for the Conservation of Nature. However, the conservation status of at least 23 species is unknown because of a lack of data.

To researchers who want to fill those knowledge gaps, Goiran recommended recruiting the help of seniors who want to be citizen scientists.

“If there is one thing I want everyone to learn from this,” she said, “it’s that you should never underestimate grandmothers.”