If a small child were to ask this question, it might be tempting to say “no, we can’t.” It would be easy to throw in something about how humans need air to breathe, or how fish have gills to live underwater, and move swiftly on (if the child allows!).
But actually, the question is not so straightforward. After all, the International Space Station exists, so we know that with the right support systems, humans can live in places that don’t naturally have breathable air. And they can do so for quite a long time.
The same is true underwater. So actually, the answer to the question is: yes, humans can live under water.
And it’s not an idle question. Achieving a sustained human presence at the bottom of the ocean is the key to expanding the next great frontier of human knowledge.
How humans can live underwater
DEEP is working to enable a new era of oceanic exploration, building on knowledge developed over more than six decades. In the 1960s, missions like Conshelf and Sealab proved that people can live underwater for days, weeks, or even months at a time.
The subsequent decades have seen many similar missions (I took part in one myself in 2016), each of which has added to our understanding of the marine environment and how humans cope under sustained high pressure (both literal and psychological).
Saturation
The basic principle that allows humans to live underwater is called saturation. Here’s how it works. Once a diver has been at a particular depth for a long enough period of time, their body will become ‘saturated’.
That means the body has absorbed all of the dissolved gases it’s going to at that pressure. The tissues in the body are in equilibrium with the partial pressures of the inert gases present in the diver’s breathing gas (for example, nitrogen in air, or helium in heliox).
The diver will still need to go through a long decompression to safely return to the surface, letting those gases release slowly to minimize the risk of decompression sickness, also known as ‘the bends’.
But once saturation is reached, the diver can stay at the bottom for days, weeks, and months without needing any additional decompression time. All they need is a place to stay down there and the basics to sustain life (food, water, oxygen).
Subsea habitats
The habitats of the 1960s onwards have got the job done, but technology has advanced significantly since the last human-occupied habitats were built decades ago.
One of DEEP’s goals is to develop a subsea habitat fit for the 21st century, one that is suitable not just for professional divers with many years’ experience, but which, with some training, can also be used by scientists and researchers.
How living underwater will lead to scientific breakthroughs
The advantage of having researchers live in a subsea habitat is it gives them a sustained presence on the bottom of the ocean. This will allow for continuous observation of the sea outside the habitat, as well as much longer dives than are possible using scuba methods from the surface.
A subsea habitat can be maintained at the same pressure as the surrounding water, so researchers living underwater can spend hours diving outside of the habitat collecting data and conducting observations.
By contrast, recreational diving from the surface typically allows for 30 to 60 minutes of time on the bottom, depending on the depth.
Technical diving from the surface allows divers to stay down longer and/or go deeper, but this type of diving still has relative time restrictions based on decompression limits and gas supply.
In saturation diving, scientists can use this extra time underwater to pursue a wide range of projects, from conservation efforts like restoring coral reefs to finding marine peptides that could be used for pharmaceuticals.
But our new generation of habitat will also provide another unique benefit. We’re designing our Sentinel habitat system so that it can be used as a laboratory, as well as a living space.
Putting labs at the bottom of the ocean means samples collected from the surrounding environment, or biological samples from the habitat’s crew, can be processed at depth without undergoing the pressure changes from taking them up to the surface, which could alter their composition.
Yes, humans can live underwater!
These are just some of the reasons being able to live underwater is important for humanity. Increasing our access to the ocean is necessary to understand and protect it better.
But to return to the original question: yes, humans can live under water, they have done it many times before, and DEEP is working on enabling more people to live underwater, starting in the very near future.
You can follow DEEP’s progress via our newsroom.