A study reveals that to this day, only a tiny fraction of the ocean floor has been visually recorded. Although it covers two-thirds of the planet’s surface, the deep seafloor remains an unknown territory.

The study, published in the journal Science Advances, notes that less than 0.001% of this vast oceanic space has been observed through imagery. In other words, we have only seen—using cameras and submersible vehicles—an area about one-tenth the size of a small country like Belgium. It’s like trying to understand what a large city looks like after only seeing one of its neighborhoods.

The work, led by oceanographer Katherine Bell and an international team of researchers, compiled and analyzed more than 43,000 records of deep-sea dives conducted with remotely operated or crewed submersibles from 1958 to the present, aimed at visually documenting the ocean floor at depths greater than 200 meters.

According to the researchers, the findings are both surprising and concerning. After decades of underwater exploration, the surface effectively observed through images does not exceed 3,800 square kilometers, an insignificant figure considering that the deep ocean floor covers more than 335 million square kilometers.

deep ocean unexplored
Deep-sea dive activity, 1958–2024. Credit: Katherine L.C. Bell et al. / GEBCO bathymetry

More than 65% of all visual observations were concentrated in waters near just three countries: the United States, Japan, and New Zealand. Moreover, 97% of all dives were carried out by operators from only five nations—those three, plus France and Germany.

This bias is also reflected in the types of ecosystems that have been observed. For example, most dives focused on underwater canyons and steep slopes, leaving aside vast flat regions like abyssal plains. One of the most studied canyons, Monterey Canyon off the Pacific coast of the United States, was the site of nearly 3,530 dives, while more than 9,000 submarine canyons around the world have never been visited by a camera.

In addition, decade after decade, dives have become increasingly shallow. In the 1960s, more than half exceeded 2,000 meters in depth, while in the last decade analyzed, that proportion dropped to just 26%—despite the fact that the majority of the ocean floor lies between 2,000 and 6,000 meters below the surface.

deep ocean unexplored
Polymetallic nodules on the ocean floor near Hawaii. Credit: Public domain / NOAA Office of Ocean Exploration and Research, 2015 Hohonu Moana

This means that from a scientific perspective, we are building our understanding of the planet’s largest ecosystem with an extremely small and biased sample. We are making decisions about conservation, deep-sea mining, or carbon capture based on data that barely scratches the surface, the authors warn.

And the deep ocean is not a cold desert—it harbors ecosystems rich in biodiversity, many of which were discovered thanks to images taken during these dives. From hydrothermal vents that led to the theory of life without sunlight, to colonies of giant mollusks living in symbiosis with bacteria, each dive has revealed surprises. It has even been discovered that certain minerals can generate oxygen without the need for light, which could change our understanding of the origin of life on Earth and on other planets.

Many of these discoveries happened by chance, driven by commercial interests or scientific curiosity. The most recent case is the Pacific region known as the Clarion-Clipperton Zone, rich in minerals. There, as a result of studies for possible resource extraction, hundreds of new species were discovered, and it is estimated that thousands more remain undiscovered.

The study proposes a more equitable and representative global exploration strategy, aimed at filling knowledge gaps and enabling fairer and more effective management of deep-ocean resources. The challenge is so monumental that even if a thousand submersible vehicles were deployed today, working at the current pace, it would take more than 100,000 years to visually observe the entire deep seafloor just once.

SOURCES

Katherine L. C. Bell et al., How little we’ve seen: A visual coverage estimate of the deep seafloor. Sci.Adv. 11, eadp8602(2025). DOI:10.1126/sciadv.adp8602

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