The deep sea stretches out like a forgotten continent, hiding more secrets than any desert or jungle. Despite covering over two-thirds of our planet, humans have only directly seen a minuscule fraction of it—about 0.001% of the deep seafloor, an area comparable to the size of Rhode Island. That figure, confirmed by a comprehensive study published in Science Advances, is based on more than 43,000 documented dives since 1958.

Beneath 200 meters, where light gives way to darkness, a realm teeming with bizarre life unfolds. We've caught glimpses of creatures like the black seadevil anglerfish and throat-toothed gulpers, as The Sun reports. But these glimpses are rare, and our views are clustered almost entirely near wealthy nations. Over 65% of visual records come from waters near the U.S., Japan, and New Zealand.

Less than 0.001% of the deep sea has been visually observed.

The Deep Sea’s Role in Life on Earth

This unexplored abyss isn’t just strange—it’s essential. The deep sea absorbs about 90% of the excess heat and 30% of the carbon dioxide caused by human activity, acting as Earth’s climate stabilizer. Without it, global temperatures would be unrecognizable. As reported in TIME, the ocean is our most vital buffer against planetary warming.

This matters more than ever as debates grow about opening the deep sea to mining for rare minerals. While policy pushes forward, understanding lags far behind. Scientists from the Ocean Discovery League caution that we still lack the baseline data to predict or repair potential damage caused by such activities.

The explored area of the deep sea is about the size of Rhode Island.

A Biased Glimpse of a Global Frontier

The little we have seen is far from representative. According to The New York Times, nearly all recorded deep dives have occurred in shallower coastal waters. Explorers have repeatedly visited known locations like the Mariana Trench or Monterey Canyon, while entire regions, such as the Indian Ocean, remain mostly uncharted.

That skew matters. The ocean floor isn’t uniform. It hosts hydrothermal vents, cold seeps, abyssal plains, and undersea mountains, each harboring unique ecosystems. These features often support life forms adapted to extreme conditions—creatures that may hold answers to everything from climate adaptation to cancer treatments.

Why Seeing Matters

While sonar and mapping tools help form rough outlines, only visual imaging reveals the nuanced complexity of these habitats.

Bringing samples up from the crushing depths often destroys them. Instead, photos and video are how scientists identify species, observe behavior, and understand ecological relationships.

And those visuals have already transformed our understanding of life on Earth. In 1977, cameras revealed ecosystems around hydrothermal vents that survive not on sunlight, but on chemosynthesis—a discovery that rewrote biology textbooks and inspired new theories about life’s origins, as outlined in Scientific American.

Most of the ocean’s volume lies below 200 meters of depth.

Missed Discoveries and Future Threats

Despite their significance, areas like abyssal plains—vast, deep regions that cover more of the ocean floor than anything else—remain woefully underexplored. The dives we’ve made have prioritized accessible or already intriguing locations. This limited scope means that sweeping conclusions about the ocean's biodiversity are being made with dangerously little data, NPR reports.

This isn’t just a scientific blind spot—it’s a policy problem. With growing interest in seabed mining, including recent executive actions to fast-track operations, we may be rushing into irreversible harm without ever understanding what we’re risking. As BGR notes, 32 countries have already called for a pause on mining, citing the sheer lack of research.

Creatures like anglerfish and throat-toothed gulpers thrive in the dark.

A New Frontier Waiting Beneath

Our planet’s largest biome remains almost untouched. Visual documentation, according to researchers, would take more than 100,000 years to complete at the current pace, unless technological breakthroughs accelerate access and lower costs.

But change is possible. Expanding affordable tools—remotely operated vehicles, tethered cameras, and autonomous submersibles—could allow more countries to participate in exploration. This global effort could yield a deeper, truer understanding of Earth’s most mysterious frontier.

Given what we’ve learned from just 0.001% of the deep sea, the possibilities waiting in the remaining 99.999% are hard to imagine—and too valuable to ignore.