For one week in January, passengers aboard Le Boreal, a cruise ship operated by French company Ponant, soaked up Antarctica's wildlife. They stood on the ship's decks to marvel at orcas, or killer whales, swimming seamlessly in groups.

They stayed up late to watch humpback whales perform bubble-net feeding, working together to scoop up schools of fish in one swift movement.

Hiking on the continent, they saw penguins waddling down "penguin highways" and nursing their young. On small boats, they got up close to leopard seals sunbathing on floating pieces of ice.

Through every adventure, guests took hundreds, if not thousands, of photographs, recording each scene from different angles and zooming in on the animals.

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They were doing so not just to show off on Instagram but also to contribute meaningfully to science.

Those who captured detailed pictures of whales sent them to Happywhale, an organisation that tracks the migratory patterns of whales through photo submissions using the unique markings on the animals' tails.

"It's just like tagging, but it doesn't harm the animal," said Ted Cheeseman, founder of Happywhale. "Getting answers to scientists' questions takes a huge amount of data. Because of these photos, it seems likely we will be successful."

This is what citizen science is all about.

Scientists are limited by time and money. A single day of research in Antarctica, for example, costs an average of US$50,000 ($74,759). They also can't be everywhere in the world at once. So a growing number of research groups have turned to the public, including tourists, for help.

Why not use travellers, with their iPhones and cameras and desire to take a lot of photos, to collect evidence?

It's also a win for tourists who get to engage more deeply with their surroundings while on vacation.

"You can be on deck enjoying the views while also being part of something greater than you," said Alejandra Nuñez-de la Mora, a Mexican bioanthropologist who was a naturalist on Le Boreal. She taught passengers how to contribute to science.

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"It's a hands-on approach."

Since Happywhale launched in 2015, the initiative has collected 150,000 photographs of whales in 40,000 encounters.

Those photographs aren't just going to Cheeseman, who is completing his PhD in marine biology at Southern Cross University in Australia.

Scientific institutions, including the Cascadia Research Collective in Washington state and the International Whaling Commission, charged with the conservation of whales and the regulation of whaling, rely on them.

"We're burning a lot of fuel to go to Antarctica," Cheeseman said. "It makes these trips more meaningful and valuable if everyone can see the data and learn something from it."

Science also benefits when wide populations are interested in projects, said Nuñez-de la Mora.

"We are lucky to have people on these voyages who are in positions of power or influence," she said. "You never know who will decide they want to get involved."

Protective policies could come from these projects; so could funding.

Participating in a citizen science project can become a habit.

One of Happywhale's most frequent contributors is Deana Glenz of Santa Cruz, California. She finds the experience so rewarding she selects holiday spots only if they include whale watching.

In January, she flew to Guerrero Negro, Mexico, to spot humpback whales. In March, she headed to the Dominican Republic to swim with them.

She enjoys the challenge.

"You are standing on a boat that is moving, trying to capture a clear photo of an animal that is also moving," she said. "It's super hard."

She's paid such careful attention, she estimates she can identify 350 whales just from seeing their patterns. She's also seen the same whale in different places around the world.

"When I see a whale often, I give it a nickname," she said. "There is one that I call Heart String. She has a marking that looks like a heart pendulum."

Cheeseman finds inspiration in the fact that so many of his contributors are teenagers and children.

"If you can turn on a kid, you never know what is going to happen," he said. "We make sure to send contributors notifications when their whale has been found in other parts of the world to keep them engaged."

The US Forest Service has projects across the country aimed at families. With the Alaska Bat Monitoring Project, for example, families mount ultrasonic microphones to their cars before they drive into the forest. Children can later listen to the bat calls that they've captured.

Organisations have made it their focus to steer tourists to citizen science opportunities.

GoAbroad.com, a search engine for travel opportunities, has an entire section of its website that lists biological research volunteer programmes. The National Geographic Society has a citizen science project search for people of all ages and Earthwatch Institute connects travellers to scientific research expeditions that need extra hands.

"Machines have gotten better, but science still needs human eyes," Nuñez-de la Mora said. "We'll take as many eyeballs as we can get."