Last year, my colleagues and I went on an expedition to the deep trenches around Japan. Having already found the Mariana snailfish in 2014—thought to be the deepest ever—we had a hunch that with more exploration and a better understanding of things like temperature, the Japanese trenches would host a fish at even greater depths.

After another 63 deployments of our deep-sea cameras, bringing our total to about 250 across the globe, we hit the jackpot.

We found what is likely a new species of fish in the Izu-Ogasawara Trench and filmed it many times at depths between 6,500 and 8,000 meters. Then, at a staggering 8,336m, a rather unassuming little juvenile slowly swam past the camera, oblivious to the fact it had just become the deepest fish on record.

Much more than monsters

If you ask someone what the deepest fish in the world looks like, they will probably conjure up an image of a scaly, black, stealthy creature with bioluminescent lures, large fangs, spiny fins and demonic eyes lurking in the depths waiting to strike at unsuspecting victims. It would be nothing like the shallow-water fish we eat, keep as pets, or pay to see in aquariums. It would be more the stuff of nightmares.

While these sorts of visually striking creatures do exist, they are often not that deep, or that big. Hatchet fish, fangtooth, lanternfish, dragonfish, viperfish and angler fish inhabit the mid-waters of the twilight zone (less than 1,000m deep). Many of these classically spooky monsters are actually very small and are simply enlarged in our imagination, in the absence of any sense of physical scale.