Imagine a colossal deep-sea predator in the ocean’s depths. It’s likely there’s a giant squid nearby, perhaps being pursued by an even larger sperm whale.

Yet, numerous enigmatic giant hunters roam the dark abyss, many still shrouded in mystery from science. Meet the Stydiomedusa gigantea, a name derived from Greek that means “giant jellyfish of the underworld.”

This impressive jellyfish is typically a deep crimson shade, showcasing smooth, rounded bells (or “caps”) that exceed 1 meter (3 ft) in diameter, adorned with a wavy margin.

Four ribbon-like arms extend back up to 10 meters (33 feet). To visualize, if one of these jellies were resting in a London double-decker bus, it could easily tap the driver on the shoulder.

The giant phantom jellyfish belongs to the Urumidae family, which also includes more common species like the moon jellyfish.

Unlike its relatives, the phantom jellyfish is devoid of stinging cells needed to paralyze prey. Instead, it relies on its long arms to capture small fish and zooplankton, guiding them into its mouth.

Specimens of the giant phantom jellyfish were first collected in the late 19th century, and the species received its official name in 1910.

Despite its size, only about 100 encounters with the phantom jellyfish have been documented over the years.

Rare sightings have occurred globally, spanning the Atlantic, Pacific, Indian, and Southern Oceans, primarily at extreme depths where they might roam over 6 km (4 miles) below the surface.

In 2025, researchers from the Schmidt Ocean Institute aboard the R/V Falcor were exploring the Southern Ocean following the recent calving of a giant iceberg, unveiling vast ocean regions previously inaccessible to scientists.

Using remotely operated vehicles like the Subastian, they uncovered a thriving ecosystem beneath the ice, teeming with animals such as octopuses and giant sea spiders.

They also captured stunning footage of giant phantom jellyfish gracefully floating in the water.

Interestingly, many of these elusive jellyfish are spotted by tourists rather than researchers. Luxury Antarctic cruise ships often come equipped with personal deep submersibles, allowing vacationers to venture beneath the waves.

Fortunate passengers have encountered giant phantom jellyfish, leaving behind ghostly footage on their smartphones as they resurface.

Scientific studies published in 2023 documented sightings primarily occurring near the West Antarctic Peninsula at depths ranging from 80 to 280 meters (262 to 918 ft).

For context, that’s roughly the height between Big Ben and the Empire State Building.

The reason these giant phantom jellies venture so close to the surface of Antarctica’s frigid waters remains an unsolved puzzle.

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