Of all the strange and wonderful animals that live in the deep sea, perhaps the most tantalising are the ones that are occasionally glimpsed by deep-submerged cameras, then swim off into the darkness before scientists can get a good look.
Many of these animals have never been handled by scientists, including an enigmatic squid with elbows, enormous rippling fins and tentacles like long, rippling strands of spaghetti.
Squid experts have scrutinised the available footage and generally presume these are bigfin squid, from the family Magnapinnidae. This group was described in 1998 based on a few rare specimens of squid larvae.
Nobody has ever caught an adult bigfin squid in a net, only on camera.
These adults look a lot like the larvae, but until a specimen is brought in, it’s hard to know for sure whether there actually is a link between the two.
Of course, that doesn’t stop deep-sea scientists from pondering the lives of these mysterious squid. The ‘elbow stance’ (below) is the bigfin squid’s usual way of catching prey.
They hold their arms and tentacles away from their bodies, splayed out like a spider’s legs, then bend them at 90°. The remaining portion of their tentacles trail through the water, perhaps setting up a wide net to passively snag prey.
Footage from the Tonga Trench in the Southwest Pacific Ocean in 2024 showed a bigfin squid walking its tentacles across the deep seabed. It’s possible the creature was searching for food to grab.
At one point, the squid seems to get a sticky tentacle stuck on something out of frame. It then spends a few seconds comically tugging harder and harder until it’s finally released from whatever its tentacle is stuck on and swims off.
That squid was filmed at around 3,300m (10,830ft) underwater. Another has been spotted at almost twice that depth, at 6,212m (20,380ft) in the Philippine Trench, the deepest record of any squid.
Their close relatives – dumbo octopuses, which swim by flapping fins that look like giant elephant’s ears – beat them to even greater depths. Dumbos have been seen around 7,000m (23,000ft) down.
Bigfin squid have been filmed only a dozen or so times in spots all across the ocean: off Brazil and West Africa, in the Gulf of Mexico, the Indian Ocean and elsewhere. So, it’s likely the family is widely distributed and there could be multiple species.
During surveys in the Great Australian Bight in 2015 and 2017, cameras were towed through the deep sea between 900 and 3,000m down (approx 2,950 to 9,840ft). Bigfin squid passed the cameras on five occasions. It was the first time they’d been seen in Australian waters.
These squid look impressive close-up on camera with tentacles many times longer than their bodies, but they’re not actually that big. The bodies of the squid filmed in Australia ranged between 6 and 15cm long (approx 2 to 6in), their tentacles stretching no more than 1.5m (almost 5ft).
But there’s always a chance that bigger bigfin squid are still out there, lurking somewhere in the vast deep-sea, hiding just off camera.
To submit your questions, email us at questions@sciencefocus.com, or message our Facebook, X, or Instagram pages (don’t forget to include your name and location).
Check out our ultimate fun facts page for more mind-blowing science
Read more:
