Deep sea mystery: 99.999% of Earth's ocean floor still remains unexplored

A new study finds that humans have visually explored just 0.001 per cent of the deep seafloor - leaving vast areas unknown and raising concerns about biodiversity, climate, and deep sea mining

We have explored towering mountain ranges, mapped deserts, and even sent robots to map volcanoes — but when it comes to the deep ocean, we’re still in the dark. A new study has revealed just how little of the ocean floor we have actually seen with our own eyes. 

A study published in Science Advances analysed data from 43,681 deep-sea dives conducted since 1958 and found that humans have visually examined a mere 0.001 per cent of the ocean beds. That’s roughly the size of Rhode Island or one-tenth of Belgium.

  The ocean’s average depth, about 12,080 ft (3,682 m), makes it virtually inaccessible without advanced submersible technology.  While around 26.1 per cent of the seafloor has been mapped as of June 2024, visual documentation remains exceptionally limited.

“This small and biased sample is problematic when attempting to characterise, understand, and manage a global ocean,” said Susan Poulton, a researcher at the Ocean Discovery League and co-author of the study, in an email to Gizmodo.

 

An unknown world await below

The unexplored seafloor holds immense potential for scientific discovery. According to the National Oceanic and Atmospheric Administration (NOAA), an estimated two-thirds of the ocean’s 700,000 to 1 million species (excluding microbes) have yet to be identified or described. The limited visual data leaves significant gaps in understanding marine biodiversity and how these ecosystems interact with the planet. 

Nearly two-thirds of all visual observations have occurred within 200 nautical miles of just three countries: the United States, Japan, and New Zealand. Most of the dives have been carried out by institutions from these nations, along with France and Germany. This geographic skew limits the global picture of deep-sea ecosystems. 

“Imagine trying to tell the story of critical environments like the African savanna or the Amazon rainforest using only satellite imagery and DNA samples without ever seeing what lived there,” Poulton said. “It wouldn’t paint a very complete picture.” 

The research also highlights a focus on shallow waters — less than 6,562 ft (2,000 m) deep — despite the fact that most of the ocean floor lies beyond that depth. Regions such as canyons and escarpments are disproportionately studied, while vast expanses like abyssal plains and ridges receive little attention.

 

Deep ocean’s crucial role in Earth’s systems

According to the researchers, better understanding the deep ocean is vital. These regions influence climate patterns, oxygen generation, and even medical discoveries. Yet, humanity has barely begun to investigate them visually. 

Some breakthroughs have come through commercial exploration. For instance, studies of the Clarion-Clipperton Zone — a site of potential deep-sea mining — has led to the identification of hundreds of new species and even novel oxygen-producing mechanisms.

 

Mining threatens unstudied ecosystems

The timing of the study coincides with US policy moves that could escalate threats to these fragile habitats. The US President Donald Trump administration’s efforts to accelerate deep-sea mining have raised alarms among scientists. Recently, researchers discovered organisms living beneath the seafloor, expanding our understanding of where life can exist. Such lifeforms may be at risk before they are even formally identified. 

 

Call for a global deep-sea exploration strategy

The authors emphasise that understanding Earth’s largest biome will require broader participation. More countries, institutions, and technological innovations must be brought into the fold. Without a shift in approach, the researchers estimate it could take more than 100,000 years to visually explore the deep seafloor at the current pace. 

They call for a “fundamental change in how we explore and study the global deep ocean”, according to a statement from the American Association for the Advancement of Science. 

Until then, critical decisions about climate, biodiversity, and marine policy are being made based on a surprisingly narrow understanding of the ocean’s depths. Expanding our reach into this mysterious realm could reshape our knowledge of the planet — and unlock scientific discoveries still waiting in the dark. 

 

  What is deep sea mining?

Deep sea mining is the process of extracting valuable minerals such as copper, nickel, cobalt, and manganese from the ocean floor at depths greater than 200 m. These minerals are found in polymetallic nodules, sulfide deposits near hydrothermal vents, and cobalt-rich crusts on underwater mountains. Mining involves robotic vehicles that collect these resources, which are then transported to the surface for processing. Driven by rising demand for metals used in batteries and renewable energy, deep sea mining is seen as a potential solution to depleting land resources, but it raises significant environmental concerns.