Scientists have paid close attention to an area off Japan recently.
They noticed a light source coming from deep blue waters.
Closer inspection revealed that this formation looked more crystalline than a biological specimen.
But there were two mysteries connected to this formation.
Inside this structure, they found another animal whose existence completely defied all expectations. Some likened this animal to one living in a castle made of glass.
What was this strange deep-sea formation, and what was the mysterious creature?
A journey into one of the ocean’s least explored worlds
Large parts of the ocean’s deep are unexplored.
Few people have ever seen these environments firsthand.
Today, scientists are discovering more species and ecosystems that have never been seen before.
In 2025, researchers joined an expedition to explore the poorly studied Nankai Trough and Shichiyo Seamount Chain.
This was achieved using a crewed submarine.
During their time below the surface, the team gathered hundreds of samples from the seafloor. From these samples, they identified over three dozen new species and likely many others that will require further examination.
What the deep ocean keeps hidden from view
The researchers added new names to the scientific record. They also showed us how large portions of Earth’s biggest environment are still unknown.
According to Ocean Census, scientists confirmed dozens of new species and identified others for naming.
The researchers also found much greater diversity in certain deep-sea environments. This suggests that many ecosystems in the deep seas remain much more biodiverse than we thought earlier.
In certain cases, scientists even came across richly populated communities of species.
The environments had hardly ever been scientifically studied prior to the expedition.
These new finds help researchers learn how life exists in some of the harshest conditions on our planet.
Large areas of the deep ocean have never been closely studied by scientists. Many species likely remain undiscovered in habitats that have barely been explored.
And among all of the findings from this project, two were exceptional.
The secret to success that lies behind the Crystal Castle
A so-called “Crystal Castle” was simply a glass sponge.
Glass sponges contain highly complex frameworks composed of silica, which is similar to glass.
The sponge had a transparent chamber framework and a castle-like appearance. Because of this, researchers named it a “castle.”
Dalhousiella yabukii, a newly discovered bristle worm, was found within the structure. This species was identified at a depth of nearly 800 m (2,600 ft) on a volcano off the coast of Japan.
The relationship between the two organisms appears to be symbiotic, with both benefiting from each other.
The predator waiting in the darkness
Researchers involved in the larger Ocean Census program made another discovery. They found a predatory sponge commonly referred to as a “death ball”.
Most sponges filter feed on organic matter found in the water around them.
However, this particular species actively hunts down prey.
Researchers noted that it employs hooks to catch small crustaceans, which it then consumes.
Although it may appear unusual, this unique predator was discovered at a depth of almost 3,600 m (12,000 ft).
These findings illustrate just how varied and different deep-sea organisms can be. Many are unlike the creatures most people envision when thinking about ocean ecosystems.
The findings remind us that there are many bizarre forms of life yet to be found on Earth.
With continued exploration of the deep ocean, researchers continually discover more examples of structures resembling crystal castles. Predators behaving differently from typical sponges represent another example.
Some discoveries continue to challenge our understanding of life below the ocean’s surface.
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