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Just after 10:00 a.m. on January 6, 2023, in the Southern Ocean some 1,100 kilometers south of Argentina, Matthew Mulrennan’s underwater camera captured a one-of-a-kind sighting: there, 176 meters beneath his vessel, a lone squid was propelling itself through the frigid water. With its outstretched vermillion tentacles, see-through body, and faint blue bioluminescent glow, this 12-centimeter-long squid is, potentially, the first colossal squid ever filmed in its natural environment.

Video captured off Antarctica nearly 200 meters deep below the surface shows what might be a juvenile colossal squid living freely in its natural environment. It’s possible this is not a colossal squid but instead another kind of closely related glass squid. Video courtesy of Matthew Mulrennan/Kolossal

Mulrennan, a marine scientist and founder of the California-based nonprofit Kolossal, has been working since 2017 to record footage of wild colossal squid. Cephalopod experts are convinced Mulrennan filmed some sort of glass squid, the scientific family to which colossal squid belong. But they remain unsure whether it was a young colossal, an adult Galiteuthis glacialis, or a previously unknown species in the closely related genus Taonius.

The Antarctic water where Mulrennan’s team spotted the squid was full of marine snow, giving the video a grainy quality reminiscent of the first photos of another little-known cephalopod: the giant squid.

Although both cephalopods are so elusive they’re practically legendary—and often compared to the mythical kraken—colossal squid have bigger, heavier bodies and slightly shorter tentacles than their giant brethren. While giant squid were first photographed and filmed in their natural habitat in 2004 and 2012, respectively, the only sightings of colossal squid have come from corpses or animals dragged up to the surface.

Until, perhaps, now.

Colossal squid were first scientifically described by zoologist Guy Robson in 1925 after a sperm whale washed up in the Falkland Islands with two colossal squid tentacles in its stomach. Since then, the massive animals have rarely been caught, photographed, or even seen. That’s a striking feat for a creature longer than a cargo container with eyes the size of volleyballs. As adults, colossal squid are Earth’s largest invertebrates. They eat Patagonian toothfish (also known as Chilean sea bass) and are hunted by sperm whales. When they’re young, colossal squid seem to venture closer to the ocean’s surface, where they’re picked off by penguins, albatrosses, seals, and Patagonian toothfish. Little else is known about their behavior; most clues are derived from fishing line nibbles, examinations of predators’ stomachs, and the occasional squid corpse that washes up on a beach.

William Reid, a marine biologist at Newcastle University in England, was lucky enough to get up-close with a colossal squid after fishers unexpectedly pulled one up in 2005 near South Georgia Island, located between Antarctica and South America. Although its several-meter-long mantle was too heavy to salvage, Reid’s incomplete 200-kilogram specimen revealed how the hooks and suckers that line the squid’s arms can pop off, giving the animal an impressive grip but also offering easy detachment from prey and predators.

In the depths of the ocean where little light penetrates, Reid suspects colossal squid are ambush hunters that wait patiently for prey to wander within reach, then use their long arms to stuff their catches into their beaks. He says the squid’s giant eyes may be adept at seeing bioluminescence, which could alert them to hungry sperm whales coming their way.

Colossal squid have been documented a few other times, too. Soviet fishers caught and photographed the first whole colossal squid in 1981 off eastern Antarctica. In 2003, fishers from New Zealand snared a dead 300-kilogram juvenile colossal squid in Antarctica’s Ross Sea, and then, in 2007, they pulled up a live 500-kilogram adult from a depth of 1,500 meters. And in 2008, Russian scientists caught one farther west in the Dumont d’Urville Sea.

But no one has ever seen a colossal squid living, undisturbed, hundreds of meters below the surface where it naturally dwells. And, as Reid emphasizes, because colossal squid tend to collapse under their own weight when dragged from the highly pressurized deep sea, studying them in their natural environment is the only way to see both their behavior and fully intact anatomy.

That’s why, from December 2022 to April 2023, Mulrennan and his crew set off on four multiweek trips from Ushuaia, Argentina, aboard the Ocean Endeavour, a tourist-packed expedition vessel operated by Intrepid Travel. Sailing alongside roughly 200 curious tourists, Mulrennan and the Kolossal team traveled to the South Shetland Islands, South Georgia, the Antarctic Peninsula, and other areas below the Antarctic Circle in search of the oversized squid.

While passengers slept and disembarked on day trips to see penguins, whales, and Antarctica’s icy terrain, the researchers—including Jennifer Herbig, a doctoral candidate at Memorial University in Newfoundland and Labrador—took turns dropping a tethered underwater camera from one of the ship’s gangways into the freezing water below.

“We’d put the camera in the water at midnight or 1:00 a.m., be up until 4:00 or 5:00 a.m., and then have to get up at 6:00 or 7:00 a.m.,” Herbig says. With the camera dangling as far as 400 meters underwater, it became a near-constant effort to keep it from getting hooked on sea ice and disappearing into the deep.

In total, the team captured 62 hours of high-definition footage. Along with their prospective colossal squid, the scientists spotted a giant volcano sponge—animals thought to live up to 15,000 years—and dozens of other deep-sea Antarctic species.

It was challenging work made easier by the ship’s other passengers, who brought the scientists cookies and hot chocolate during long nighttime deployments. Herbig, for her part, cherished the tourists’ interest. “They could just peek over our shoulders and see what we were doing, so we got to explain some of the science,” she says.

“Every day on the ship, I was asked, ‘Did you find the squid?’” Mulrennan recounts. “People really want to know more about these large kraken-like species”—especially the ship’s chef, who kept joking about cooking the squid if they found it.

Whether the video Mulrennan’s team captured turns out to be a juvenile colossal squid or not—that final determination depends on continued examinations by squid experts at New Zealand’s Auckland University of Technology—the Kolossal researchers aren’t finished with their quest just yet.

While last year’s expedition relied largely on using an underwater camera to film close to the noisy vessel, the team hopes to revisit Antarctica as soon as November 2024, armed with a much broader suite of tools.

Mulrennan is looking to upgrade from one underwater camera to as many as a dozen, which he can deploy simultaneously, and he wants to add remotely operated cameras that would enable filming farther from the boat. Another option for improving their technique, says Herbig, would be to get longer camera cables so they can peer even deeper into the colossal squid’s frigid domain. Herbig adds that they could also bring equipment to analyze environmental DNA and measure biomass, helping the team study the abundance of creatures that share this deepwater habitat.

With a tattoo on his left arm commemorating zoologist Guy Robson’s 1925 sighting of a colossal squid, Mulrennan hopes to lead or inspire a verified underwater filming of a live, wild colossal squid by 2025.

“If finding the giant squid was like landing on the moon, then finding the colossal squid’s going to be like landing on Mars,” he says.