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Scientists exploring a submarine canyon off Western Australia encountered a spiral-shaped siphonophore estimated at about 45 metres (150 feet) long—nearly 50 metres from end to end. The 2020 sighting, made from the Schmidt Ocean Institute’s RV Falkor and ROV SuBastian at roughly 600 metres depth, may represent the longest animal ever measured, but no formal world record has been ratified.
What was the ghostly giant?
The animal was a siphonophore, a colonial organism built from many genetically identical units called zooids. Rather than functioning as independent animals, the zooids remain physically connected and specialize in different jobs. Some capture food, while others handle propulsion, steering, reproduction or defense. Their coordination allows the colony to behave as one integrated organism.
The specimen is probably in the genus Apolemia, whose members are known for long, tangled forms. Its exact species has not been established, so describing it as a probable Apolemia is more accurate than assigning a definitive species name.
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Western Australian Museum scientist Nerida Wilson described the sight as “like a rope on the horizon. You couldn’t miss it.” The colony was arranged in a large spiral, a posture interpreted as a feeding configuration rather than a permanent body shape.
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How the siphonophore feeds
Siphonophore tentacles carry stinging cells. When the colony spreads into a spiral, those tentacles can create a broad capture barrier through which crustaceans and fish are intercepted. Specialized zooids then coordinate the handling and digestion of prey.
This feeding strategy helps explain why the animal can appear enormous without having a massive, whale-like body. Much of the measured length is an extended chain of connected zooids and tentacles suspended in the water, not a thick central trunk.
Is it really the longest animal ever?
The best-supported estimate is approximately 45 metres (150 feet). The Guardian reported that figure in 2022, and the Australian National Maritime Museum’s campaign retrospective also records a 45-metre siphonophore. A 2026 Daily Galaxy report repeats the 150-foot estimate and describes the specimen as a possible longest-ever animal.
Researchers inferred the length from the remotely operated vehicle’s travel track and video geometry. Because the animal was observed in the water rather than recovered and measured on a deck, the estimate was not initially presented as a formally certified record. The careful description is therefore “a candidate for the longest animal ever measured,” not a confirmed world-record claim.
A future photogrammetric analysis or taxonomic study could adjust both the length and the identification. The phrase “nearly 50 metres” is a rounded headline description of the approximately 45-metre estimate.
How can a siphonophore exceed a blue whale’s length?
The comparison depends on what “length” means. A blue whale is one vertebrate body with a continuous skeleton, organs and muscle mass. A siphonophore is a colony whose specialized zooids extend along a trailing, flexible structure. Measuring the full colony is closer to measuring the entire length of a connected chain than the solid body of a single animal.
| Animal | Body plan | What the length represents | Feeding pattern | Evidence for this comparison |
|---|---|---|---|---|
| Deep-water siphonophore | Colony of specialized zooids acting as one organism | Extended colonial structure, including the connected chain and trailing parts | Coordinated tentacle barrier carrying stinging cells | About 45 metres estimated from submersible track and video geometry |
| Blue whale | Single vertebrate body | Continuous animal body | Active vertebrate feeding rather than a colonial capture wall | Not measured in this expedition |
| Portuguese man o’ war | Colonial siphonophore | Colonial form that can extend beyond a compact central body | Surface-drifting tentacle system | Included as a body-plan comparison, not part of the 2020 measurement |
| Ordinary jellyfish | Single medusoid animal | Individual body and attached structures | Drifting or swimming capture surface | Included as a contrast with a colonial siphonophore |
The comparison is consequently about architecture as much as scale. A longer end-to-end measurement does not mean the siphonophore has more mass, volume or muscular power than a whale.
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The ROV encountered the colony in a deep submarine canyon off Western Australia, in the Ningaloo Canyon expedition area, at about 600 metres depth. Submarine canyons cut through the continental shelf and connect coastal waters with the deep Indian Ocean, creating steep walls, currents and food pathways that support specialized communities.
The wider region belongs to a network of major underwater canyons. Parks Australia describes Perth Canyon Marine Park as Australia’s largest underwater canyon, covering 7,409 square kilometres and reaching 5,000 metres depth. That measurement describes Perth Canyon Marine Park, not the exact point where this siphonophore was filmed, but it illustrates the scale of the surrounding deep-sea landscape.
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What the 2020 expedition found
The expedition used the Schmidt Ocean Institute’s RV Falkor and ROV SuBastian to investigate areas that cannot be observed reliably from the surface. The title-matching expedition account reports 20 ROV dives, depths of up to 4,500 metres and 181 hours of exploration.
That account also reports up to 30 new underwater species or likely new records, including giant hydroids, glass-sponge communities, a long-tailed sea cucumber and a bioluminescent octopus squid. The Australian National Maritime Museum’s retrospective gives a broader count of more than 50 potential new species for the wider 2020 Australian campaign. Those figures refer to different scopes and should not be combined into one total.
Wilson said scientists expected the deep areas to be diverse but had been “blown away by the significance of what we have seen.” Lisa Kirkendale of the Western Australian Museum said the specimens extended depth and range records for many species and would become an important addition to Western Australian museum collections.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why a single video encounter matters
Deep-canyon ecosystems remain difficult to sample. A remotely operated vehicle can document fragile colonies in place, record their behavior and collect selected specimens without requiring a crewed submersible to remain at depth. The resulting video, specimens and collection records can support species descriptions, environmental-DNA studies and long-term monitoring of marine parks.
The observation also shows why a headline measurement should be treated as a scientific estimate. The colony’s flexible shape, changing posture and great length make direct measurement difficult. Preserving the original track, video geometry and any collected material allows later researchers to test the estimate as analytical methods improve.
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What remains unresolved
- The exact species has not been confirmed; probable Apolemia is the cautious identification.
- The approximately 45-metre length is an estimate, not a formally ratified longest-animal record.
- The spiral was interpreted as a feeding posture, although the encounter was a short observation rather than a complete behavioral study.
- Additional photogrammetry or taxonomic work could revise the animal’s measured length and classification.
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