OK so there is a fish, a real actual fish swimming around in the Pacific Ocean right now, with a completely see-through head. Like a glass dome. Like it's wearing a tiny fishbowl on its own face. And inside that dome sit two tubular green eyes that rotate, tracking food floating above like tiny periscopes, and I need you to stop whatever you're doing and look at this thing immediately.

It's called the barreleye fish, and scientists had known about it for decades but only from dead specimens pulled up in nets, and the transparent head gets destroyed in the process. So everyone just assumed its eyes were locked staring upward, permanently. Then in 2009 the Monterey Bay Aquarium Research Institute filmed one alive in the deep using a remotely operated vehicle and the footage revealed the truth: the eyes rotate. The fish can point them straight up to catch silhouettes of prey against the faint light from above, then swing them forward when it goes in for the eat. The dome is transparent so the eyes can see through it. its own skull is a window.

And it gets weirder! Those two glowing green orbs that look like eyes on the front of its face? Not eyes. Those are its nostrils. The actual eyes are inside the head, behind the fake ones. It has basically evolved a disguise on its own face to confuse you, a human reading about it almost two decades later, which I choose to take personally.

The tubular eye shape is the part that breaks the textbook rules. Most vertebrates have big rounded eyes that trade light-gathering power for a wide field of view, but the barreleye went all in on a different strategy: long, narrow, ultra-sensitive tubes built to snatch every hint of faint light and bioluminescent glint in the deep. Down there in the midnight zone, where sunlight basically doesn't exist, this fish hoovers up whatever stray glow it can find with its two green telescopes.

The 2009 video was the first time anyone had ever seen a living barreleye intact, which means for all those years our entire picture of this animal came from specimens that had lost their most important feature in the net. Generations of scientists going "huh, weird that the eyes can't move" when the answer was the eyes move great, you just broke the evidence.

I've covered a lot of deep-sea creatures for this site and I will never run out of delight for them, and the barreleye is exactly why. Evolution just keeps solving the same problem, seeing in the dark, in ways nobody would dare to make up. A fish with a glass skull and swiveling telescope eyes that hides its real eyes behind its fake ones. Nature didn't have to go this hard and it did anyway. Joy is worth documenting, and so is this little weirdo.