Due to the pressure difference to the surface we have seen very little of the deep ocean even though it covers more than 70% of the planet’s surface. After nearly 70 years of submersible exploration specialists estimate we have observed less than 0.001% of the deep seafloor.
That percentage sliver corresponds to roughly the size of Rhode Island. That does not mean the scientists know nothing about the ocean, but it does expose a major blind spot as deep-sea ecosystems draw a growing interest from both science and industry together. How could we study something we can’t even see?
Humans have only glimpsed the deep seafloor
We have been so focused on studying outer space for so long that we overlooked the ocean, but that is changing. A study published in May 2025 reviewed 43,681 records of submersible dives dating back to 1958 in order to understand what we really know about the deep sea. The team focused on direct visual observations below 200 meters, a depth range that includes a seafloor region covering about 66% of Earth’s surface.
The study proved that we are very far from having substantial data. Most of the data gathered is skewed by the fact that it has been done on specific locations, which means the results can’t even be replicated in other areas. The samples we have are too tiny and the ocean too vast.
Mapping the ocean is not the same as seeing it
To map the broad shape of the seafloor the scientists have used ship-based sonar, gravity models and satellites. Those tools reveal all the different landscapes, from trenches and ridges to underwater plains and mountains, but they are not powerful enough to reveal the details of those habitats.
To see what is really going on down there we have to get closer, and that’s the challenge. A well placed camera near the bottom can capture pictures of coral communities, hydrothermal vents, animal behavior, sediment texture, fields of mineral-rich nodules and most likely things we still have to discover. Those image fragments could help understand how habitats work, if they are damaged or even if they are different from what images from afar have shown.
Most deep-sea views come from only five countries
The study also found the observations were not spread around the world. About 67% were made within 200 nautical miles of the United States, Japan and New Zealand. At the same time 97% of the recorded dives were conducted by those same 3 countries plus France and Germany.
The concentration is a reflection of how expensive ocean work is. All the technology surrounding deep-sea diving is specific and expensive, so only a limited number of nations and institutions have the resources to start or keep such endeavors.
Why this knowledge gap matters now
The deep ocean is no longer a distant topic discussed just by oceanographers. It now sits at the center of debates that include a range of themes: from biodiversity, biotechnology, carbon cycling and climate change to more practical areas such as subsea cables (that are so fundamental to our communications systems), and the possible mining of mineral-rich abyssal plains.
In order to go further we need more data. Not only visual data, but all kinds of data. How are the chemical measurements? Can we find and study biological samples? What can we find analyzing acoustic data? How about genetic data of species, what can it show us? Images do provide a clear record, but the vastness of data that can be gathered is immense. There’s much that can still be done.
The physics of deep-ocean exploration are unforgiving
The low percentage the study found is not a sign of idleness. New studies are being done but the task is not an easy one. Below 200 meters the sunlight fades quickly, pressure rises by roughly one atmosphere every 10 meters and vehicles must work in cold darkness while carrying their own lights and cameras.
Remotely operated vehicles often rely on cables and acoustic systems but radio waves do not travel well through seawater, adding another layer to the already hard task. Even a carefully planned dive can take so much time since crossing a tiny patch of seafloor is not the same as walking on the surface.
Scientists are asking for changes
The study calls for broader participation by coastal and island nations whose waters and knowledge have often been underrepresented in deep-sea research. The prices are steep but many developed countries have ocean knowledge enough to collect benefits through scientific exploration.
After nearly 70 years the clearest conclusion is that the deep ocean has been only glimpsed and our view remains astonishingly narrow.
