A Giant from the Deep: Scientists Film Bus-Sized Jellyfish off Argentina

More than eighty percent of the world’s oceans remain largely unexplored, a vast frontier where new discoveries still emerge with surprising regularity. Now, an international team of scientists has captured rare footage of one of the ocean’s most mysterious inhabitants—a giant phantom jellyfish so large that researchers described it as “the size of a school bus.”

The remarkable sighting took place during a research expedition aboard the vessel Falkor, which traveled along the Argentine continental margin from Buenos Aires south toward Tierra del Fuego. Using remotely operated vehicles, scientists filmed the elusive species Stygiomedusa gigantea at a depth of about 250 meters.

This deep-sea jellyfish is rarely observed, partly because it inhabits midwater depths far below the reach of most conventional research. Its bell can reach extraordinary dimensions, and its ribbon-like oral arms—often mistaken for tentacles—can extend up to ten meters, drifting through the water like long, flowing banners.

The discovery was made during a broader scientific survey of deep-sea ecosystems off Argentina’s coast. Researchers reported unexpectedly high biodiversity in the region, documenting coral communities and identifying what may be 28 previously unknown species, including worms, snails, and sea anemones.

“We didn’t expect such high biodiversity in the Argentine deep sea and are thrilled to see it so full of life,” said expedition lead scientist Dr. María Emilia Bravo of the University of Buenos Aires.

Beyond the striking imagery, the expedition also gathered extensive chemical, physical, and biological samples. According to Dr. Melisa Fernández Severini of the Argentine Institute of Oceanography, these samples will help scientists better understand how deep-sea ecosystems function and how vulnerable they may be to environmental change.

For researchers, the giant phantom jellyfish is more than a spectacle—it is a reminder of how much remains unknown beneath the waves. Each expedition reveals that the deep ocean is not an empty darkness but a living, complex world, still holding secrets that continue to surprise even the most experienced explorers.