Whether it's to escape environmental collapse or to explore new, unknown territories, the drive to establish human colonies in places other than on Earth has been gaining momentum in recent years.
And while proposed bases on the Moon or Mars might get all the headlines, there's another equally hostile and largely unknown location a lot closer to home that explorers are looking towards: the bottom of the ocean.
This is by no means a new idea. Starting with French oceanographer Jacques Cousteau in the 1960s, people have been building and spending limited amounts of time in underwater habitats for decades.
More recently, NASA has been sending people to the Aquarius Reef Base, a research facility on the ocean floor just off the coast of Florida, since 2001. Located 20m (approx 65ft) below the surface, scientists, engineers and prospective astronauts typically spend 7-14 days in the module.
New technology is making the prospect of longer-duration stays underwater possible, though, and British company, Deep, is employing it to develop habitats specifically for that purpose. The tech may be up to the task, but the real question is, are we?
Above the atmosphere, below the sea
Humans are relatively weak. We don't do well without oxygen or sunlight, and we're not big fans of major changes in pressure. In other words, we're not necessarily the best candidates for life at the bottom of the sea.
That's not to say we're incapable of living in hostile environments.
Since the year 2000, astronauts have lived for extended periods aboard the International Space Station (ISS), a habitat assembled in conditions that are just as challenging as those we would experience underwater.
Various astronauts have clocked up over 300 consecutive days aboard the ISS, but cosmonaut Valeri Polyakov holds the record with the 437 days he spent aboard Russia’s Mir space station between 1994 and 1995.
The thing is, astronauts who’ve spent long periods in space often arrive back on Earth with a variety of health concerns, including reduced bone density and muscle atrophy. But what about the prospects for people looking to live underwater?
The longest case study is Rudiger Koch, a German aerospace engineer who spent 120 days living in a capsule (the top of which is pictured below) submerged 11m (36ft) beneath the surface of the Caribbean Sea between 2024 and 2025.
Koch reported no health concerns when he emerged and celebrated with champagne and a cigar.
In second place is Prof Joseph Dituri. He spent 100 days in a lodge at the bottom of a 9m-deep (30ft) lagoon in Florida, in an effort to understand the physical and psychological health effects of underwater life.
Dituri performed daily tests on himself both while submerged and after returning to the surface. And, other than a new-found height, he wasn’t just fine, he was better.
He noticed improvements in his sleep, cholesterol levels and inflammation levels. His stem cell count increased, as did his testosterone and performance on cognitive tests.
In fact, Dituri emerged with a biological age (a measure of how well your body is ageing) 10 years younger than his chronological one. He was, however, a little over 1cm (about 0.5in) shorter, as the pressurised environment inside the lodge had caused him to shrink.
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A step towards life underwater
With such a small bank of evidence, we don’t have a solid grasp on what the prospects might be for people looking to spend extended periods underwater. That’s where Deep comes in.
The ocean technology and exploration company is developing two habitats to find out and has set the ambitious goal of having a permanent presence beneath the ocean by 2027. The company has even taken over a flooded quarry in Gloucestershire to use as a test bed for its underwater habitats.
Deep is working on two habitats: the Vanguard, a smaller module for three people on short-term stays under the sea; and the Sentinel, a 16m (52ft) capsule that they hope will serve as a longer-term habitat – complete with living spaces, bedrooms and research facilities – and can house researchers at depths of up to 200m (656ft) for 28 days at a time.
The goal is to allow researchers to spend longer living underwater and enable them study the ocean floor as well as the effects of living underwater. But getting people to these depths is challenging.
“The risky part for a diver is going down and coming back up,” says Dr Dawn Kernagis, director of scientific research at Deep. “They’re breathing compressed gas and the pressure is changing, increasing the risk of decompression sickness (DCS), where bubbles can form in the blood."
Though most cases of DCS (commonly known as ‘the bends’) are mild, the most severe can affect the brain, spinal cord, the respiratory system and the circulatory system.
To minimise the risk of it occurring, Deep aims to keep researchers staying in the Sentinel ‘saturated’ – a state where the body has absorbed all of the dissolved gases it would at a particular pressure. Essentially, this is the body reaching a new underwater equilibrium.
“Saturation tanks, like the ones we’re building, allow divers to go to these lower depths and stay there much longer because they can adjust to the pressure. This takes their time [at these depths] from hours to a month or so,” says Kernagis.
Deep plans to closely monitor researchers at Sentinel during their stay to better understand the long-term physical and psychological ramifications of deep-sea living.
These stays will lay the groundwork for progressively longer ones, from weeks, to months, and maybe even years. And who knows, in the not- too-distant future, some of us could find ourselves living in a modern Atlantis.
About our expert
Dr Dawn Kernagis is the director of scientific research at Deep, the UK-based ocean technology and exploration company. She has been published in various scientific journals, including Journal of Clinical Oncology, Proceedings of the National Academy of Science and Circulation.
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