The legend of the Kraken, a massive sea creature said to drag entire ships beneath the waves, has been traced by scientists to the real existence of the giant squid. For centuries, stories from Scandinavian sailors described an animal large enough to be mistaken for an island. While many historians dismissed these accounts as exaggeration, the discovery of enormous squid specimens in the 1800s provided concrete evidence that the myth was likely based on a genuine, rarely seen animal.
The giant squid, scientifically known as Architeuthis dux, is now recognized as one of the largest invertebrates on Earth. Female giant squid can reach approximately 13 meters in length from the back of the body to the tip of their two long feeding tentacles, with some examined specimens stretching close to 18 meters. Males are generally smaller, reaching around 10 meters. The main body typically remains under 2 meters, with most of the length coming from the long tentacles.
For most of human history, no one had observed a giant squid alive. All scientific knowledge came from dead specimens that washed ashore or were found in the stomachs of sperm whales. This changed in 2004, when Japanese researchers photographed a live giant squid attacking bait at a depth of about 900 meters in the North Pacific Ocean. In 2012, the first video footage of a live adult in its natural habitat was captured in the same region, using a submersible.
Giant squid generally live at depths between 300 and 1,000 meters, in a zone where almost no sunlight penetrates. Their large eyes, among the largest of any animal, are believed to have evolved not for spotting prey but for detecting the shapes of approaching predators, such as sperm whales, from a great distance in near-total darkness. These depths are still far above the bottom of the Mariana Trench, which sits nearly 11,000 meters below the surface.
Another species, the colossal squid (Mesonychoteuthis hamiltoni), surpasses the giant squid in weight. It lives in the cold waters of the Southern Ocean around Antarctica, typically at depths ranging from a few hundred meters to more than 2,000 meters. Confirmed specimens have weighed close to 500 kilograms, with some scientists estimating that the largest individuals, known only from beaks found in sperm whale stomachs, could weigh up to 700 kilograms. This makes it the heaviest invertebrate documented on the planet.
The colossal squid also has the largest eyes of any known animal, measuring roughly 27 centimeters across. Unlike the giant squid, which has rows of small teeth lining its suckers, the colossal squid has sharp, rotating hooks on its arms and tentacles, making it a more heavily armed hunter. These hooks can swing in a full circle, allowing the animal to lock onto struggling prey from almost any angle, a feature not seen in other known squid species.
For decades, scientists had only examined dead or dying colossal squid pulled up from fishing lines. In April 2025, a remotely operated vehicle working for the Schmidt Ocean Institute near the South Sandwich Islands filmed the first confirmed footage of a live colossal squid in its natural environment. The footage showed a juvenile drifting through open water, providing the first proof of what the species looks like alive.
Sperm whales, the largest toothed predators on the planet, hunt deep-sea squid. Males can reach lengths of around 18 meters. They dive to depths between 600 and 1,000 meters on normal feeding trips, staying underwater for around 45 minutes. Tagged individuals have been recorded diving past 2,000 meters, with some documented dives reaching close to 2,250 meters.
Sperm whales manage these dives by shutting down nearly every non-essential body function. Digestion stops, and blood is redirected from the skin and arms to the heart and brain. The whale can hold its breath for over an hour on the deepest dives. A large, oil-filled organ in its head called the spermaceti organ may help control buoyancy and focus sound waves for hunting in total darkness. Scars on the skin of many sperm whales, left by the hooks and suckers of squid, are among the only physical evidence that these underwater battles occur.
The true record for the most extreme survivor at the bottom of the Mariana Trench belongs to a much smaller animal. The supergiant amphipod, known scientifically as Alicella gigantea, grows to more than 30 centimeters, roughly 20 to 30 times larger than its relatives. Researchers have recorded it at depths ranging from around 3,890 meters down to 8,931 meters, placing it firmly inside the hadal zone, the deepest parts of ocean trenches. Recent genetic studies suggest a single global population of this species may be spread across more than half of the world’s oceans, with nearly identical DNA found in trenches thousands of kilometers apart.
Scientists are not entirely certain why this species grows so much larger than every other amphipod. Leading theories point to the crushing pressure and near-freezing cold of the deep sea, conditions that may allow cells to grow larger and animals to live much longer than their shallow-water relatives, a pattern known as deep-sea gigantism. Some studies have also found unusually large genome sizes in this species compared to its smaller relatives.
The deepest confirmed living fish on the planet is the Mariana snailfish (Pseudoliparis swirei). In 2014, cameras lowered into the Mariana Trench near the Sirena Deep recorded a pale, soft-bodied fish swimming at a depth deeper than any living fish had been filmed before. Researchers formally described it as a new species in 2017. The Mariana snailfish has no scales and a soft, almost jelly-like body built to handle pressure. A natural chemical called trimethylamine oxide builds up inside the cells of deep-sea fish like this one, keeping proteins stable so they do not get crushed by the surrounding water pressure. The deeper a fish lives, the more of this chemical its body carries.
No confirmed giant squid, colossal squid, or sperm whale has ever been documented at the true bottom of the Mariana Trench. These animals live thousands of meters above the floor. What has been confirmed at hadal depths are creatures like the supergiant amphipod and the Mariana snailfish, animals built small and strange, shaped by pressure into forms unlike anything in folklore.
Less than a quarter of the ocean floor has been mapped in detail, and scientists continue to describe new species from hadal depths on a regular basis. The 2025 footage of a live colossal squid, the first ever captured, is one recent example. The real story of the Mariana Trench is not a monster waiting in the dark. It is a world of record-breaking animals, some heavier than a car, some diving deeper than any human machine built before 1960, and some so different from anything at the surface that classifying them took scientists decades. The deepest place on Earth continues to demonstrate that the documented truth is stranger and more interesting than the legend.
