On a March day in one of the most remote corners of the planet, a myth rose from the deep.
SuBastian did it again! Roughly 600 meters beneath the icy waves near the South Sandwich Islands, the remotely operated submersible floated past a ghastly creature. It shimmered, translucent, with wide, glowing eyes and delicate fins barely perceptible in the darkness.
It was the first confirmed sighting of a live colossal squid (Mesonychoteuthis hamiltoni) in its natural habitat. And to the astonishment of the crew aboard the Schmidt Ocean Institute’s research vessel Falkor (too), the squid was a juvenile, only about 30 centimeters (nearly a foot) long. At full size, it could grow to 7 meters and weigh up to 500 kilograms, making it the heaviest invertebrate on Earth.
“It’s exciting to see the first in situ footage of a juvenile colossal and humbling to think that they have no idea that humans exist,” said Dr. Kat Bolstad, a marine biologist at Auckland University of Technology who helped confirm the finding.
The Abyss Stared Back
This sighting—captured on March 9—came during a 35-day Ocean Census flagship expedition designed to find new species in the Southern Ocean. The initiative is a collaboration between the Schmidt Ocean Institute, the Nippon Foundation-Nekton Ocean Census, and GoSouth, a joint project with researchers from the University of Plymouth, GEOMAR, and the British Antarctic Survey.
The team launched the submersible SuBastian to explore the waters near the South Sandwich Islands, a chain of volcano-dotted islands far enough from civilization that the closest humans were aboard the International Space Station. The squid casually popped up on the livestream unexpectedly.
The crew sent the footage to leading squid experts, including Bolstad and Dr. Aaron Evans, another specialist in the elusive glass squid family. Both confirmed the identity of the animal by spotting a telltale feature: hooks along the middle of its eight arms, a unique hallmark of the colossal squid.
“This is honestly one of the most exciting observations we’ve had,” Bolstad said during a press conference. “We get to introduce the live colossal squid to the world as this beautiful, little, delicate animal.”
Solving a Century-Old Mystery
The colossal squid was first identified in 1925, based on remains found in the stomach of a sperm whale. In the hundred years since, nearly everything we’ve learned about it has come from carcasses—most of them half-digested.
“Even to this day, the enormous invertebrates still straddle the line between legend and reality,” noted the Natural History Museum in 2022.
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Well, not anymore.
Unlike its better-known cousin, the giant squid, the colossal squid lives deeper, swims slower, and is built like a tank. Shorter in length, but broader and heavier, it wields hundreds of rotating hooks on its arms and two long tentacles tipped with barbs. Its eyes are the largest in the animal kingdom, up to 27 centimeters (~ 10 inches) across—wider than a basketball.
These eyes aren’t just for finding prey in the dark. They may have evolved to detect predators like sperm whales, which routinely dive into the squid’s abyssal domain. Some whales have been found with scars likely inflicted by a squid’s defensive hooks.
“For 100 years, we have mainly encountered them as prey remains in whale and seabird stomachs and as predators of harvested toothfish,” Bolstad noted. This live juvenile, she said, now offers a “starting place” to understand the creature’s life cycle—an enormous gap in marine science.
Sea Discoveries Coming in Packs
The March expedition wasn’t the only one to make headlines. Just weeks earlier, another team aboard the Falkor (too) recorded the first footage of a glacial glass squid (Galiteuthis glacialis) in the Bellingshausen Sea, near Antarctica. That sighting, captured at 687 meters, revealed the squid striking a pose with its arms gently hovering above its head—an eerie, cockatoo-like gesture.
Together, these back-to-back discoveries hint at a hidden bounty in the deep Southern Ocean.
“These unforgettable moments continue to remind us that the ocean is brimming with mysteries yet to be solved,” said Dr. Jyotika Virmani, executive director of the Schmidt Ocean Institute.
So far, SuBastian has captured first-ever footage of at least four squid species, including the Ram’s Horn squid (Spirula spirula) and Promachoteuthis, a deep-sea rarity only described in recent decades. A fifth new squid species may also be pending confirmation.
The sightings are also made possible by the telepresence network that beams footage live to scientists across the globe.
“It’s incredible that we can leverage the power of the taxonomic community through R/V Falkor (too) telepresence while we are out at sea,” said Taylor.
Colossal Squid: Giant of the Deep
The colossal squid’s story is only just beginning. Here are a few startling facts about this mysterious titan:
- Heaviest invertebrate ever recorded: Estimates suggest up to 700 kg (1,500 lbs) and 10 meters (33 feet) in length.
- Eyes the size of basketballs: At 27 cm across, they’re the biggest eyes of any known animal, likely evolved to detect massive predators like sperm whales.
- Cannibalistic tendencies: Juveniles may hatch in shallower waters to avoid being eaten by larger, adult squids of their own species.
- An arsenal of hooks: Not only do their arms and tentacles sport rotating hooks for grabbing prey, they’ve also left scars on sperm whales—evidence of fierce undersea battles.
- Slow, deliberate swimmers: Despite their size, colossal squids are not fast. They conserve energy in the frigid waters of the bathypelagic zone—between 1,000 and 4,000 meters deep.
- Tiny beginnings: Females may produce up to 4.2 million eggs, each just 3 mm wide. Hatchlings begin life near the surface and slowly sink deeper as they grow.
- Shrouded in mystery: Due to the difficulty of reaching their habitat and their extreme rarity, the squid’s exact population, lifespan, and behaviors remain largely unknown.
- Not endangered: For now, the colossal squid is listed as a species of Least Concern—not because it’s common, but because human interaction with it is so rare.
One century ago, the colossal squid seemed like a sea monster out of myth—its only traces surfacing from the bellies of whales. Today, it glides through our screens, fragile and glittering, as a reminder that some of Earth’s greatest marvels remain unseen.
