We've Explored Nearly 70 Years of Ocean Depths and Seen Almost Nothing

A Frontier Hiding in Plain Sight

Humanity has sent cameras to the Moon, Mars, Venus, and the outer planets — but on Earth itself, there is still a larger frontier that has barely been looked at directly. That frontier is the deep ocean floor, and a landmark pair of studies from the Ocean Discovery League has now put a staggering number on just how little we actually know about it.

Since 1958, researchers compiled 43,681 records of dives deep enough to see the seafloor below 200 meters, and all of that visual exploration adds up to less than 0.001% of the deep ocean floor. That is an area roughly the size of Rhode Island, or about a tenth of Belgium, set against the part of the planet that lies below the reach of sunlight and covers about 66% of Earth's surface. Nearly two-thirds of the world is deep ocean, and our direct view of its floor is barely a pinprick.

Maps Are Not the Same as Seeing

The study is not saying that scientists have no maps of the ocean floor. Satellite gravity data, shipborne sonar, and global bathymetry projects have traced the broad architecture of seamounts, trenches, ridges, abyssal plains, and continental margins — those tools tell researchers a great deal about shape and depth. But visual observation is different. A camera, a crewed submersible, or a remotely operated vehicle can reveal whether the seafloor is bare sediment, living coral, hydrothermal vent, sponge field, nodule plain, carcass fall, or a habitat that has never been described.

Visual imaging is critical for studying deep-sea organisms, as bringing them to the surface often results in their demise due to pressure changes. Nearly 30% of documented observations occurred before 1980, often producing only low-resolution black-and-white imagery. And even the modern observations we do have are deeply skewed. Sixty-five percent of all in-situ visual seafloor observations were within 200 nautical miles of only three countries — the United States, Japan, and New Zealand — and 97% of all dives were conducted by just five countries: the United States, Japan, New Zealand, France, and Germany.

A Biased Sample of a Vital Ecosystem

This geographic concentration has led the oceanographic community to base much of its understanding of the deep ocean on an incredibly small and unrepresentative sample. As threats to the deep ocean accelerate — from climate change to deep-sea mining — this gap becomes a critical problem for both science and policy. The deep ocean sustains diverse ecosystems and provides essential services, including oxygen production, climate regulation, and critical pharmaceutical discoveries. Making sweeping decisions about an ecosystem this important, based on a sample this tiny, is a serious problem.

Given that not all dive records are public, the researchers assert that even if these estimates are off by a full order of magnitude, less than one-hundredth of 1% of the seafloor would have any visual records. The knowledge gap, in other words, is not a matter of rounding errors. It is profound and deliberate acknowledgment of how much remains unseen.

A Roadmap to Change That

In April 2026, the Ocean Discovery League announced the launch of the Global Deep Sea Exploration Goals — an ambitious international effort to visually explore 10,000 strategically selected locations across the deep seafloor. When completed, the initiative will nearly double the number of unique seafloor locations ever visually observed and produce the first globally representative visual dataset of the deep ocean floor, unlocking new discoveries about biodiversity, ecosystem function, and environmental change.

Achieving a globally representative effort cannot be accomplished through improved sampling design alone — it also requires a redistribution of opportunity, tools, and training. The strategy identifies the scientific gaps that indicate where capacity building and new deployments are most urgently needed, including regions that are often remote from prior exploration efforts and have had limited access to deep-submergence tools. By focusing efforts on these underrepresented areas, the global community can help close critical knowledge gaps while broadening participation in deep-ocean science. For a planet that is mostly ocean, it is long overdue.