10 Deep Sea Creatures That Should Not Be Allowed

Somewhere beneath you right now, at a depth where the last blue photon gave up and went home, a fish is watching the world through the roof of its own transparent skull. It is fine. That skull is a beautifully adapted answer to an optical problem you will never have.

Evolution, handed total darkness, crushing pressure and almost nothing to eat, returns solutions that look like a dare. Here are ten animals whose biology should not be permitted. All ten are real. Without further ado.

1. The Barreleye Fish

Macropinna microstoma was described in 1939 by the American biologist Wilbert McLeod Chapman, and for seventy years everybody had it wrong, because specimens arrived in nets with their heads wrecked. The living fish wears a clear fluid-filled dome over its skull. Those two glowing green orbs inside it are the eyes. The dark spots on its face are nostrils.

In 2009 MBARI researchers showed the tubular eyes rotate. It stares up through its own forehead for silhouettes, then swivels forward to supervise its own mouth. MBARI has logged more than 5,600 dives across its 600 to 800 metre range and seen one nine times.

2. The Goblin Shark

Described in 1898 from Japanese waters, the goblin shark is the last member of a family roughly 125 million years old. Pink rubbery skin. A flat snout full of electroreceptors, and jaws folded into a pocket underneath until required.

Kazuhiro Nakaya of Hokkaido University analysed NHK footage of two feeding goblin sharks for a 2016 paper in Scientific Reports. The jaws fire forward at up to 3.1 metres per second and travel 8.6 to 9.4 percent of body length, the fastest and furthest protrusion measured in any shark. Until 2026 every video came from a shark already hauled up on a line. That year a University of Hawaii at Manoa team published two wild sightings in the Journal of Fish Biology, one at 1,237 metres near Jarvis Island, one at 1,997 metres down the Tonga Trench slope.

3. The Bone-Eating Snot Flower Worm

In February 2002 MBARI’s ROV Tiburon found a dead gray whale at 2,893 metres in Monterey Canyon, its bones carpeted in something red and shaggy. That something was a new genus of worm, named Osedax in Science in 2004.

Here is the part that should be illegal. It has no mouth, no gut and no anus. It bores into whale bone with acid secreted from root-like tissue, and bacteria in those roots break down the fats locked inside. Every worm you can see is female. The males never grow up, staying at essentially larval size and living by the hundreds inside a female’s tube, with harems above 600 recorded in the larger species. A relative found off Sweden in 2005 was named mucofloris, Latin for snot flower. Scientists did that on purpose.

4. The Deep-Sea Anglerfish

You know the lure. Bioluminescent bacteria, cultured in a bulb called the esca. That is the boring part. In many ceratioid anglerfishes the male is a tiny free-swimming animal with enormous nostrils and no working digestive system, whose entire career consists of sniffing out a female before he starves to death. When he finds her, he bites. Then he fuses. His tissues knit into hers, their circulatory systems join, and he degrades into a sac of testes hanging off her flank, living on her blood. In Krøyer’s deep-sea anglerfish, females can run over sixty times the length of an attached male and half a million times his weight.

A 2020 Science study from the Max Planck Institute of Immunobiology and Epigenetics explained how the graft survives. Permanently fusing species have thrown away adaptive immunity, including the rag genes that assemble antibodies and T cell receptors. They beat organ rejection by deleting the immune system.

5. The Blobfish

Psychrolutes marcidus lives off southeastern Australia and Tasmania between roughly 600 and 1,200 metres, and down there it looks like a fish. A faintly grumpy sculpin. Its body is gelatinous tissue a shade less dense than seawater, so it hovers over the mud without swimming and gets by on almost nothing.

So why does everybody think it looks like that? The photograph you have seen is a corpse. Drag that jelly up through a hundred atmospheres of pressure change and the flesh slumps into the famous sad melted face. In September 2013 the internet voted that face the World’s Ugliest Animal and made it mascot of the Ugly Animal Preservation Society. Redemption arrived in March 2025, when the blobfish took New Zealand’s Fish of the Year with 1,286 votes from more than 5,500 cast.

6. The Yeti Crab

In 2005 a submersible working a vent field 1,500 kilometres south of Easter Island brought back a blind white crustacean about 15 centimetres long, covered in silky blond fur. They called it Kiwa hirsuta, after the Polynesian goddess of shellfish.

The fur is a farm. Those bristles carry chemosynthetic bacteria feeding on vented sulphides and methane, and the crab harvests the crop with comb-shaped mouthparts. Kiwa puravida, described by Andrew Thurber in 2011 from a methane seep off Costa Rica, was filmed waving its claws over the flow, stirring fresh chemicals across the bacteria to make them grow faster. Subsistence agriculture, performed by a blind hairy crab, in permanent darkness.

7. The Vampire Squid

Carl Chun dredged one up on the German Valdivia expedition and described it in 1903 as Vampyroteuthis infernalis, the vampire squid from hell, going by the black webbing between its arms and the red eyes. The reputational damage never wore off.

It stands alone in its own order, Vampyromorphida, and lives in the oxygen minimum zone on a fraction of the oxygen found at the surface. Hendrik Hoving and Bruce Robison published its real diet in Proceedings of the Royal Society B in September 2012. It trails two long retractile filaments and collects marine snow. Discarded larvacean houses, crustacean fragments, faecal pellets, diatoms. Threaten it and there is no ink. It fires a cloud of glowing mucus from its arm tips and leaves.

8. The Giant Isopod

Bathynomus is what happens when the woodlouse under your flowerpot reaches the size of a house cat. Fourteen legs. In January 2025 researchers buying specimens from fishmongers in Quy Nhon, Vietnam described a new supergiant from near the Spratly Islands, averaging 32.5 centimetres and topping a kilogram. They named it Bathynomus vaderi, because the head looks like Darth Vader’s helmet.

Food is scarce down there, so isopods have become world-class at not eating. One at Toba Aquarium in Mie Prefecture, catalogued as No. 1, took a 50 gram piece of horse mackerel on 2 January 2009 and then refused every meal offered for five years and 43 days. Keepers found it dead on 14 February 2014. The dissection turned up no blockage, no tumour and no explanation.

9. The Gulper Eel

Described by Léon Vaillant in 1882, Eurypharynx pelecanoides is mostly mouth with a whip attached. The skull is reduced, the jaw hinge is huge, and the pharynx is a loose pouch that inflates the way a pelican’s throat does. The tail ends in a pink luminous organ that appears to work as a lure.

On 19 September 2018 the E/V Nautilus filmed one about a mile down in Papahānaumokuākea Marine National Monument. It ballooned to several times its own volume, held the shape, deflated, and swam off looking like an eel again.

10. The Dumbo Octopus

The Grimpoteuthis octopuses swim by flapping two ear-shaped fins above their eyes, which is as silly as it sounds and also efficient in water that cold and heavy. They carry no ink sac. Ink is pointless in permanent night.

In April 2019, on the Five Deeps Expedition, a lander camera recorded one foraging on the floor of the Java Trench at 6,957 metres. Alan Jamieson and Michael Vecchione published it in Marine Biology in May 2020. That is more than 1,800 metres below the old record, and the first firm evidence of any cephalopod living in the hadal zone below 6,000 metres.

Most of this is free to watch. MBARI archives its ROV footage and species profiles, and the Ocean Exploration Trust streams live dives from the E/V Nautilus at Nautilus Live. If you prefer your horrors manufactured rather than evolved, we have catalogued a few, and unlike the barreleye they ship in three to five business days.