Shark! Shark! Shark!” I could hear someone shouting, despite the water in my ears, as I waited in the chilly Nova Scotia water. My heart started racing as I stared through the bars of the shark cage and into the emerald abyss.

The plump female great white – nearly four metres long – blasted out of the depths. She grabbed the bait dangling in front of me in her powerful jaws as the scientists onboard the boat above tried to pull it away. She swam right up to the cage, and for a brief second our eyes were mere inches apart. Far from a mindless killer, I saw a fellow being, intelligent and complex.

So complex is Carcharodon carcharias – also known as white shark – that scientists are having a hard time answering some of the most basic questions about the animal’s behaviour and lifecycle. What do they eat? When and where do they mate and give birth? Where in Canada do they go? How many are even in Canada? A 2021 report from the Committee on the Status of Endangered Wildlife in Canada states simply: “The absolute population size of white shark in the Northwest Atlantic is not known.”

And now, another mystery is unfolding. Over the last five to seven years, many more white sharks have been found off the coast of Nova Scotia. It is a good news story – great whites are a species at risk – but no one can say what’s behind the increase. It could be climate change – or perhaps the sharks have always been here, and people are just becoming more aware of them?

Marine ecologist Dr Neil Hammerschlag has started a long-term monitoring program off Nova Scotia in the hopes of finding some answers – and educating the public in the process. Scientific grants for such long-term work are rare, so he’s turned to eco-tourism, establishing Atlantic Shark Expeditions to help fund his work. Today, paying guests can go out on the research vessel to look for sharks, participate in citizen science projects and, if they’re brave enough, get close to sharks in an underwater cage. Just like I did.

The expeditions’ research goals for the sharks include identifying and cataloguing individuals, tracking relative abundance trends (population numbers relative to other organisms) and “evaluating the species’ residency and space use patterns.”

Atlantic Shark Expeditions’ Captain Art Gaetan, who works with Dr Hammerschlag and has been tagging blue sharks in Atlantic Canada for decades, was one of the first people to realise just how many great whites are in Nova Scotia. Even he has a tough time putting a number on the population though.