Officially, 5% of Earth’s ocean area has been explored*. However, the real number depends on what we mean by ‘explored’. And, indeed, on what we mean by ‘ocean’.

The Seabed 2030 initiative is working to map the ocean floor. In June 2024 it reported it had charted just over 26% of the world’s underwater terrain, a remarkable achievement for a project that began in 2017.

But habitats are not two dimensional. The average depth of our oceans is 3,600m. So while it’s often said that the ocean covers more than 70% of the planet, that only takes account of the area on the surface. In terms of total space, oceans in fact make up more than 99% of the volume of Earth.

Besides, mapping the seabed is not the same as going down there and conducting research. Even where we have done that, the technology available to date has severely restricted the amount of time people can spend at depth, and so has limited the ability to conduct research and make new discoveries.

The challenges of ocean exploration

We often compare the way we explore the ocean to what it would be like if we had to explore rainforests by helicopter. We would know far, far less about our planet’s flora and fauna if all we could do was either send down unmanned vehicles or winch people down for 30 minutes (or less) at a time.

Fortunately, researchers can go into rainforests and stay there indefinitely while they conduct their research. They can also learn from those whose ancestors have lived there for millennia about, for example, which plants have medicinal benefits.

By contrast, there has until now been no way of enabling a sustained human presence in the part of the ocean known as the Blindspot Zone (spoiler alert: this is about to change).

What is the Blindspot Zone and why is it hard to do research there?

The Blindspot Zone is the depth of the ocean between 50 and 200 metres. Light penetration is lower here than it is closer to the surface, but is still sufficient to support photosynthesis. It’s a blind spot because our current technologies don’t provide efficient or sustained access to this part of the ocean.

Here’s why. There are currently only three ways humans can access the Blindspot Zone at all: going there in a submersible, diving from the surface, or something called saturation diving.

Submersibles

Submersibles allow people to stay at the same atmospheric pressure as on the surface. The big advantage of this is it eliminates the need for and risk of decompression, and so allows untrained crew to access depth.

The major disadvantages are limited dive times (just a few hours) and high cost. Submersibles systems themselves cost millions of dollars.

On top of that, their operation also requires a dive support vessel and a large surface crew, the cost of which can run to hundreds of thousands of dollars per day. This makes submersibles an impractical option for projects that require many thousands of hours at the bottom.

It also doesn’t enable humans to interact directly with the marine environment, and so precludes tasks that require human dexterity and cognitive ability.

Surface diving

Surface diving, whether from the shore or from a dive support vessel, can be done to depths of around 150 metres, but only for extremely limited time periods.

And the deeper a diver goes, the less time they can spend there because the amount of decompression time required goes up, as does the amount of time before they can safely dive again.

In practice, therefore, surface diving is effective for working dives to depths of no more than 50 metres.

Saturation diving

Saturation diving involves divers staying under pressure until the body’s tissues become saturated with the gases they absorb at that pressure. After that happens, any additional time spent at depth doesn’t require extra decompression time.

The concept of saturation diving was proven in the 1960s by programmes like Sealab and Conshelf. Today it’s used for commercial diving, particularly in the oil and gas industry.

Divers live together for weeks in a saturation chamber, pressurised to the same pressure as the target working depth, which is housed on a massive dive support vessel. A pressurised diving bell takes them from their cramped living quarters to the seabed and back again.

At the end of the mission, the pressure in the living chambers is gradually reduced over several days until it’s the same as the surface pressure and the crew can safely leave.

While this technique could theoretically be used to access the Blindspot Zone, it is impractically expensive. It also involves spending time in a not-so-pleasant living environment, which is unlikely to be conducive to groundbreaking scientific research.

Why we need better access to the Blindspot Zone and how we can achieve it

The difficulty accessing the Blindspot Zone for sustained periods represents an ongoing loss to human knowledge.

The unique conditions of marine environments have led to the evolution of organisms that produce chemicals that can’t be found on land. Some of these have been used to develop new medicines, but there will be many, many others waiting undiscovered.

The Blindspot Zone also contains all the world’s mineral, resource, and fisheries rights, 96% of coral reef systems, more than 90% of all Marine Protected Areas, and over 70% of shipwrecks, salvage, and cultural sites.

Virtually the entire continental shelf lies within the Blindspot Zone. We’re talking about an area of seabed bigger than Russia and Canada combined. The health, economic, and cultural benefits of achieving sustained human access to these areas is incalculable.

But it will take a new approach, and new technologies, to do this. That’s why DEEP was set up. We’re designing and building a new type of human habitat system, called Sentinel, that will enable researchers to live and work on the seabed for weeks or months, unlocking research opportunities that have never been possible before.

Discover the Sentinel System to find out how we’re doing it.

*According to the US National Oceanic and Atmospheric Administration.