Scientists exploring a submarine canyon off Western Australia in 2020 encountered a spiral-shaped siphonophore colony estimated at about 45 metres (150 feet) long. That makes it a candidate for the longest animal ever measured, but the figure is an estimate from submersible video and track geometry—not a formally ratified world record.
What was discovered?
The animal was filmed at roughly 600 metres below the surface during an expedition in the Ningaloo Canyon region. Schmidt Ocean Institute’s research vessel RV Falkor deployed the remotely operated vehicle (ROV) SuBastian, which encountered the gelatinous colony arranged in a vast spiral.
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Western Australian Museum scientist Nerida Wilson described the sight: “It was like a rope on the horizon. You couldn’t miss it.” The apparent rope was not one continuous-bodied animal. It was a siphonophore, a colonial cnidarian whose many units function together as a single swimming and feeding system.
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How a siphonophore can reach 45 metres
A siphonophore begins as one organism but develops into a chain or network of genetically identical zooids. Each zooid is specialized rather than self-sufficient. Some capture and digest food, others provide propulsion or steering, while others handle reproduction or defense. Their division of labor allows the colony to operate as an integrated animal.
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The observed specimen is probably in the genus Apolemia, which includes unusually long, tangled forms. Its estimated length describes the full extended colony, including trailing sections and tentacles, rather than a compact body that could be weighed or measured like a whale.
The spiral was probably a feeding posture
Researchers interpret the spiral as a feeding configuration. Siphonophore zooids deploy tentacles armed with stinging cells, creating a wide capture barrier through which small fish and crustaceans pass. Coiling the colony may concentrate that barrier while the swimming units hold the structure in place.
Is it really the longest animal ever?
About 45 metres (nearly 50 metres) is the best-supported estimate currently associated with the sighting. The Guardian reported the 150-foot estimate in 2022; The Daily Galaxy repeated it in 2026; and an Australian National Maritime Museum retrospective records the same 45-metre observation from the wider Australian campaign.
The length was inferred from the ROV’s movement and video geometry. Because scientists did not initially present a complete photogrammetric measurement or a preserved specimen, the animal should be described as a candidate for the longest animal ever measured. A later analysis could change both its estimated length and its identification.
Why its length is not directly comparable with a blue whale
| Feature | Giant siphonophore | Blue whale |
|---|---|---|
| Body plan | Colony of genetically identical zooids with different jobs | One vertebrate body with organs in a single animal |
| What “length” means | Distance across an extended, flexible colony and its trailing sections | Measured length of a solid individual body |
| Feeding method | Coordinated wall of stinging tentacles that captures drifting prey | Active swimming and filter-feeding through baleen |
| Evidence for the figure | ROV video, navigation track and geometric estimate | Direct measurements of individual whales |
A siphonophore can therefore exceed a whale in end-to-end length without approaching it in mass or volume. The comparison is biologically interesting, but it is not an equivalent contest between two similarly built bodies.
Where was the giant found?
The sighting took place in a deep submarine canyon off Western Australia, within the Ningaloo Canyon expedition area. Submarine canyons cut through the continental shelf and channel nutrients and organic material into the deep Indian Ocean, creating steep, complex habitats that are difficult to survey from the surface.
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For regional scale, Parks Australia describes Perth Canyon Marine Park as Australia’s largest underwater canyon. The park covers 7,409 square kilometres and reaches depths of 5,000 metres. Perth Canyon is a separate named canyon system, so its dimensions should not be treated as the exact location or depth of the siphonophore sighting.
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What the expedition found beyond the siphonophore
The title-matching expedition account reports 20 ROV dives, depths of up to 4,500 metres and 181 hours of exploration. It lists as many as 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 totals cover different scopes and should not be combined into a single species count.
Lisa Kirkendale, head of aquatic zoology at the Western Australian Museum, said the collected material represented “so many extensions in depth and range records for so many species” and would add an important new part to Western Australian museum collections.
Why deep-canyon discoveries matter
Most of the deep ocean remains difficult to observe, and a remotely operated vehicle can stay with a fragile colony without bringing it to the surface. The expedition produced video, specimens and collection records that can support formal species descriptions, environmental-DNA studies and future monitoring of marine parks.
Wilson said scientists expected the deep-sea areas to be diverse but had been “blown away by the significance of what we have seen.” The siphonophore illustrates why: a habitat that appears empty from above can contain a colony tens of metres long, arranged in a form that would be impossible to recognize from a brief surface observation.
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What remains uncertain
- The exact species has not been established in the available accounts; “probable Apolemia” is the cautious identification.
- The approximately 45-metre length is an estimate, not a certified record measurement.
- The spiral’s feeding interpretation is based on observed form and known siphonophore biology.
- Future photogrammetric work or a taxonomic paper could revise the length, genus or both.
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