Barreleye fish with a transparent head showing a coral reef with a diver and a turtle inside (AI-generated symbolic image)

If everyone could see inside your head – would you hide 600 meters deep too?

ByChristian

A transparent head, green eyes and a real talent for avoiding people: the barreleye fish is one of the strangest creatures in the deep sea. And it raises a rather personal question.

Imagine everyone could look inside your head. No warning, no password, no privacy. Your boss would see what you really think of his latest “brilliant idea”. Your partner would know what you actually think of the new living room decor. And your dive buddy would notice that you are thinking less about the underwater world right now than about the dinner buffet.

I wouldn’t be thrilled. And I’m the boss.

Barreleye fish: when evolution fails at privacy

Macropinna microstoma sounds like an Italian pasta shape, but it is a deep-sea fish only about 15 centimeters long, with a transparent, fluid-filled dome on top of its head. And no, the two dark spots at the front are not its eyes, they are its nostrils. The real eyes sit behind them, are tube-shaped and glow green.

For a long time, people thought these eyes were fixed, staring straight up. Then footage and observations from the Monterey Bay Aquarium Research Institute (MBARI) showed that the fish can rotate them forward. It looks up for prey, then turns its gaze ahead. A built-in change of perspective, no coaching seminar required.

What looks like a design flaw is an adaptation to a world where hardly any light arrives and bioluminescence rules. The barreleye fish isn’t badly built. It is built for an environment in which we humans would be pretty lost.

7,000 dives, eleven encounters

On October 20, 2026, MBARI filmed a barreleye fish in the Pacific off California at around 600 meters depth, and announced it on October 28. The high-resolution 4K footage is special for one reason: in about 7,000 dives with underwater robots, the species has been sighted only eleven times.

Eleven times. People who can’t get through a day without an Instagram story could learn a thing or two from that.

Is it shy of humans? There is no scientific evidence for that. The deep sea is huge, the animals are small, chance encounters are rare. But honestly: with a transparent head, I would also look for a remote address.

What would be visible in your head?

For most of us: appointments, shopping lists, annoyance about things we can’t change, and the question whether the coffee machine is still on. Plus that one thought that has been going around in circles for days. An off switch would sometimes be really handy.

I found mine. It is called diving.

When I descend, the sounds of the world above me fade away and only my breathing remains. I hover over the reef, a school of anthias dances in the sunlight, a turtle drifts by. No emails, no phone calls, no meetings. The things that felt so urgent on land lose their importance.

Yes, even underwater my head isn’t empty. Buddy, equipment and surroundings need attention. But the thought carousel slows down remarkably fast.

In those moments, anyone is welcome to look inside my head. They would find a bit of wonder, a bit of happiness, a lot of calm. And probably the thought: “Damn, it’s beautiful here.”

Diver face to face with a barreleye fish with a transparent dome head and green eyes (AI-generated symbolic image)
Symbolic image, AI-generated: two gazes, one thought. Underwater, the mind goes quiet.

You don’t have to dive 600 meters deep

You need no deep sea and no underwater robot for this. In Dahab, ten meters are enough: warm, clear water, a reef that starts right at your doorstep and a relaxed dive without any rush. That is exactly why we have lived and worked here for so many years.

Never dived before? Then this is the best moment to start. With the SSI Open Water Diver course you learn everything you need in a relaxed atmosphere with us, and you experience the Red Sea from its most beautiful side right away. If you are already a recreational diver, Dahab offers reefs, walls and dive sites that even experienced divers happily spend a few extra days on. And if you want to build your skills, we have the right specialties for you.

I invite you to try it. I promise: after your first dive, you will no longer care who is looking inside your head.

Maybe the barreleye fish has the better life

Whether our transparent friend feels something similar, we don’t know. We only know that it is perfectly adapted to its world and simply is where it belongs.

That may be the most beautiful lesson: not to deal with everything at the same time.

If everyone could see what is going on in your head, would you rather hide 600 meters deep? I say: it depends. On a hectic Monday morning, probably right away. During a relaxed dive in the Red Sea, everyone is welcome to look in.

Happy Diving!
Christian from Lagona Divers

PS: Both images in this post are AI-generated. Footage of such a rare animal belongs to the researchers who invested decades and thousands of dives in it, and it cannot simply be shared freely. If you want to see what the barreleye fish really looks like, follow the links below to the original publications. It is worth it, I stared at it for quite a while myself.

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You will find more unusual marine animals and diving stories in the Lagona Divers Blog.

Sources and further reading

Note: The sightings mentioned refer to MBARI’s documented observations, not to the worldwide population of the species.

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