Earlier this month, the good folks at the Schmidt Institute for Oceanography, unveiled the first video footage of a colossal squid. Colossal squid were first described 100 years ago, but have never been seen live. What little information we have comes from specimens that washed up on beaches or from hard parts found in the stomachs of sperm whales and other predators. For a century, we’ve known that colossal squids are the mass massive invertebrate on the planet, and yet, we’ve never seen one alive in its environment until now.
How does the planets biggest invertebrate stay hidden for a century?
The simple answer is that they are fast and we are loud.
Sampling is bias. For most of the history of ocean exploration, we were largely unaware of the role that soft-bodies organisms play in deep-sea food web. Researchers from the Challenger Expedition onwards would drag vast nets through the midwater, bringing up sharks and shrimp and and squid and, sometimes even dolphins and turtles. Plankton tows would capture the tiniest arthropods and other larva. But nets dragged through the sea are harsh, and the softest creatures, jellies and ctenophores and siphonophores and their kin, would be pulverized by the equipment.
When we were finally able to enter the sea and witness ocean biodiversity with our eyes and our cameras, we discovered a much different world than the one we had hypothesized, from counting the dead wrapped in our nets.
Imagine, for a moment, that you are a large, highly-mobile marine animal. Something with gills, that can survive indefinitely in the dark midwaters of the ocean, without needing to surface to breath. You move effortlessly through three dimensions. You almost never encounter a hard object. You world is cold. Your world is dark. And your world, until very recently, is filled with natural sounds–dolphin clicks, shrimp snaps, the rumble of icebergs. Close you eyes and visualized a world of water and twilight.
And now, the roar of hydraulic pumps. The clang of metal couplers on metal housings. The grind of gears. The electrical hum. And the light. The blinding, blazing light burning through the sea where it should not be.
An ROV. A monstrous thing descending from the world above the sea.
Do you stay or do you flee?
I would have to imagine that, if any deep-ocean animal is capable of complex thought, the experience of witnessing and ROV must be akin to humans thinking they’ve encountered a UFO. Doubly so if they witness the ROV abduct organisms from the surrounding seafloor.
This is one of the great paradoxes of ocean exploration, the tools we use to document the deep ocean are practically guaranteed to ensure that we are under sampling large, mobile fauna. Anything that can flee from the noise and light of an ROV of submersible almost certainly will. In shallower waters, we can overcome this challenge with baited remote underwater video (BRUVs), but the vastness and inaccessibility of the deep ocean means that even the most effective BRUVs will, at best, provide a snapshot of the total diversity of mobile fauna.
This is one of the most frustrating things about the current push to advanced deep-sea mining. Despite a lot of excellent environmental work, we still do not have anything close to a complete picture of what these ecosystems actually look like. At best, we have surveys of disturbed systems, with the act of exploration being, itself, the first disturbance. The limited acoustic monitoring we have from the Clarion-Clipperton zone reveals that marine mammals are far more active in the area that shipboard observations suggest.
There is a level of natural variability in the deep ocean that has never been fully categorized, not for lack of trying, but for the realities of the sheer scale and cost of deep-sea research. Long term, low-disturbance BRUVs deployed over years, rather than days or weeks, to capture how these ecosystems may change throughout the seasons, can and will reveal new and novel species. The ecosystems themselves may be very different from how we describe them, today.
There are, without a doubt, monsters in the deep sea that have never been observed.
Featured Image: This is the first confirmed live observation of the colossal squid, Mesonychoteuthis hamiltoni, in its natural habitat. The team on Schmidt Ocean Institute’s Research Vessel Falkor (too) captured footage of the 30-centimeter-long squid (nearly one foot) at a depth of 600 meters (1968 feet) using their remotely operated vehicle SuBastian during an Ocean Census flagship expedition searching for new marine life. The expedition took place in the remote South Sandwich Islands in the South Atlantic Ocean. This year (2025) is the 100-year anniversary of the identification of the colossal squid, which are estimated to grow up to seven meters (23 feet) in length.
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