Scientists Document Rare Phantom Jellyfish the Size of a School Bus in Argentina

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The deep ocean off Argentina’s coast is teeming with far more life than scientists ever imagined — and it’s also holding onto some of humanity’s trash.

An Argentinian-led expedition aboard the research vessel R/V Falkor (too) has documented 28 suspected new species along the world’s largest known deep-sea coral reef of its kind.

It also unveiled a collection of rare and remarkable sightings that are reshaping what researchers know about biodiversity in the deep waters of the South Atlantic.

The research was conducted by the Schmidt Ocean Institute.

But amid the wonder, the team also found a sobering reminder of human impact. Fishing nets, garbage bags and a well-preserved VHS tape with a Korean sticker on it, all sitting on the ocean floor in one of the most remote environments on the planet.

Photos and videos of the expedition’s findings were released by the Schmidt Ocean Institute on Feb. 3.

“We were not expecting to see this level of biodiversity in the Argentine deep sea, and are so excited to see it teeming with life,” said the expedition’s chief scientist, Dr. María Emilia Bravo of the University of Buenos Aires and CONICET, in a Feb. 3 press release.

“Seeing all the biodiversity, ecosystem functions, and connectivity unfolding together was incredible. We opened a window into our country’s biodiversity only to find there are so many more windows left to be opened,” she added.

An Expedition Spanning Argentina’s Entire Coast

Scientists surveyed deep-sea ecosystems along the entire length of Argentina’s continental margin, from Buenos Aires to waters near Tierra del Fuego.

The scope of the journey allowed researchers to document ecosystems that had never been studied at this scale, and what they found exceeded expectations at nearly every turn.

Among the 28 suspected new species are worms, corals, sea urchins, sea snails and sea anemones — creatures that have been living in the deep ocean, unknown to science, until now.

One of the expedition’s most significant discoveries was the largest known reef of Bathelia candida in the world. The reef covers at least 0.4 square kilometers — roughly the size of Vatican City.

This cold-water coral provides vital habitat for a wide range of marine life, including fish, crustaceans, octopuses and more. Scientists also found Bathelia reefs 600 km farther south than their previously known range, suggesting these corals are more widespread than researchers had understood.

Deep-sea coral ecosystems like these are considered Vulnerable Marine Ecosystems because they support high biodiversity but are threatened by human activities like bottom trawling.

A Giant Jellyfish and a Whale’s Final Resting Place

The team also documented two rare sightings that stood out even among a journey full of surprises.

One was a rare giant phantom jellyfish, a striking deep-sea creature whose arms can reach up to 10 meters — about 33 feet, or roughly the size of a school bus.

The other was Argentina’s first deep-water whale fall, found at a depth of 3,890 meters.

Whale falls occur when a whale carcass sinks to the ocean floor, creating a temporary ecosystem that feeds octopuses, sharks, crabs, microorganisms and more. These sites can sustain deep-sea life for years, serving as oases in the vast darkness of the deep ocean.

Beyond the headline discoveries, the expedition documented additional deep-sea ecosystems that help paint a fuller picture of Argentina’s underwater world.

Scientists observed ancient bubblegum coral gardens — composed of Paragorgia arborea — at around 3,000 meters depth. The team also identified a large active cold seep about 1 square kilometer in size.

Cold seeps are areas where methane and chemicals leak from the seafloor. These chemicals fuel microbes that, in turn, support animals such as clams, mussels, tube worms and more.

Each of these ecosystems represents a distinct community of life, thriving in conditions most people would consider inhospitable.

Unfortunately, not everything the team found was natural.

Researchers also observed human debris scattered across deep-sea areas, including fishing nets, garbage bags and a well-preserved VHS tape with a Korean sticker on it.

The durability of plastics allows trash to persist even in remote deep-ocean environments, a stark reminder that human activity reaches even the most isolated corners of the planet.

What It All Means for Science

The expedition collected an unprecedented number of chemical, physical and biological samples.

These samples will help scientists understand ecosystem connections, biodiversity patterns, and how vulnerable these deep-sea environments may be.

Scientists say the findings reveal that much of Argentina’s deep-sea biodiversity remains unexplored — and that what has been found so far only scratches the surface.

“We collected an unprecedented number of chemical, physical, and biological samples that will be used to understand connections in our waters for years to come,” said Dr. Melisa Fernández Severini of Instituto Argentino de Oceanografía and CONICET, per the Feb. 3 press release.

“These samples represent a unique opportunity to understand not only how extraordinary these extreme ecosystems are, but also how vulnerable they can be,” she added.

Dr. Jyotika Virmani, executive director of the Schmidt Ocean Institute, emphasized the broader significance of the work.

“With every expedition to the deep sea, we find the Ocean is full of life—as much as we see on land, and perhaps more because the Ocean contains 98% of the living space on this planet,” Virmani said.

The findings underscore a central truth about the ocean: for all we have explored, there remains a vast underwater world that is still largely unknown — full of life, full of surprises, and in need of protection.