How Humans Learned To Live Under Water


Every American knows the names Mercury, Gemini and Apollo. At the dawn of the space age, another frontier was under exploration, too—although it never had the fanfare or funding that the astronauts received.

Deep in the ocean, aquanauts, imbued with their own sub-aquatic strain of the Right Stuff, began building the undersea version of a space station. Here is how decades of scientific and technological breakthroughs led these pioneering divers to the mission that just wrapped up at the Aquarius Reef Base.

The Secret To Staying Down

For most Americans, Aquarius isn’t a household name, and neither is the revolutionary approach to deep-sea diving that made it all possible, a concept called saturation diving. Sat diving, for short, is as significant to underwater exploration as supersonic flight is to the sky. Without it, there would have been no Aquarius, and no Sealab, or any of the other sixty or so underwater bases that came before it.


Saturation diving was initially dismissed as impractical if not fantastical. But it turned out to be the key to pushing beyond the long-accepted limits that prevented divers from going very deep or staying down for very long. They typically had to resurface after a matter of minutes, rather than the hours and days now commonplace at a base like Aquarius. Sat diving was a risky and uncertain proposition back in the late 1950s, when an obscure U.S. Navy doctor named George Bond began running laboratory tests with animals and then simulations with human volunteers. He wanted to find out whether this newfangled approach to diving could actually work—or if it would just cause painful internal injuries and, possibly, unceremonious death.

If it did work, though, then divers—soon to be known as aquanauts—could do a variety of jobs outside of a pressurized, climate-controlled undersea base, much as astronauts do at the International Space Station. The development of sat diving was not just a matter of getting the gear right but of getting the science right. During an ordinary dive—whether using modern scuba or the iconic hardhat system, with the bulbous helmet and heavy canvas suit—a diver’s blood and tissues become partially saturated with the gas he or she breathes. That gas could be the 79-percent nitrogen, 20-percent oxygen mix of regular air, or a different recipe as required on deeper dives. Either way, at the end of a dive, divers have to undergo the process of decompression, a carefully structured timetable to allow for the gradual release of those absorbed gases before surfacing. Without adequate decompression, a diver’s innards will bubble like an open can of soda, which is what causes the painful and quite possibly lethal phenomenon popularly known as “the bends.”

With saturation diving, as the name implies, a diver’s blood and tissues are allowed to become completely saturated with the gases being breathed. Back in Dr. Bond’s day that sounded like a death sentence, in part because it would take about a day to become saturated, and then decompression would be interminable—if it was even possible to safely rid a body of all that absorbed gas. No one knew. But Bond and his acolytes figured out that a saturated diver could remain at depth indefinitely. Decompression could be postponed for hours, days, or even weeks, if a saturated diver had a properly equipped habitat. It would have to have circulating air that was also pressurized to match the water pressure outside., and a hatch in the floor that could open to allow aquanauts in and out. Bond and his team invented this type of habitat, which had one caveat: Surfacing could not be an option. Once saturated at depth, a diver could go deeper, but a direct rise to the surface, without decompression, well, that would be bad. Decompression would be possible—at Aquarius today, the process takes about 18 hours. The researchers showed how one long decompression was a small price to pay to live and work for days on the seabed.

The Undersea Village

The legendary Jacques Cousteau and the American inventor Ed Link picked up on the concept of saturation diving, and began trying out some rudimentary habitats of their own designs in 1962. Cousteau called his habitat project “Conshelf,” short for Continental Shelf Station, and came up with a pair of more advanced Conshelf habitats the following summer. He liked to call it the world’s first undersea village. The depth was similar to Aquarius, where the seabed is about sixty feet below the surface, which puts the habitat entry at about 45 feet. By 1964, following the favorable results of Bond’s lab experiments, the U.S. Navy put up a little money—about $200,000—to create a prototype habitat of its own, called Sealab I. Nearly two hundred feet below the surface, about 25 miles southeast of Bermuda, the base became the first major demonstration of the concept of saturation diving at sea. By conventional, short-duration diving standards, that depth—and the fact that the four Sealab aquanauts were equipped to stay down for three weeks—was off the diving charts of the era. There were a few close calls, but it all seemed to work.

The Navy was impressed enough to invest in a new project: Sealab II. Beginning in 1965, off the coast of La Jolla near San Diego, it became a triumphant showcase for saturation diving and sea dwelling. A Sealab III was built—and by then, some scientists envisioned a continuing series of habitats, like NASA’s space programs. But in 1969, a few months before the first moon landing, tragedy struck Sealab III, killing a diver at the astonishing depth of six hundred feet. As the space program received ever more money and media attention, the Navy quietly allowed Sealab to fade away.

It came down to the scientists who had taken part in Sealab to keep the vision of sea bases alive. Forget the Navy’s idea of a military use—they saw a unique research opportunity, as aquanauts had so much more time than divers to observe, conduct studies, run experiments, accumulate data, and generally get better acquainted with the marine environment. In the meantime, NASA had its own plans—to that agency, an underwater outpost seemed like a good analog to living in space. The agency co-funded two projects, Tektite I and II, which reinvented habitat architecture with some unusual designs. At a depth of 45 feet, Tektite was a shallow operation compared to Sealab, which had been pushing toward the thousand-foot mark. But four aquanauts lived there for a record-setting 60 days, proving that when studying marine life is concerned, duration can be as important as depth.

An Open Frontier

Underwater exploration through the 1970s gave way to wild mix of designs under public and private funding. First, the National Oceanic and Atmospheric Administration (NOAA) bought a 43-foot tank-like habitat called Hydrolab, a little lab that began as a project of Florida Atlantic University in the 1960s when Sealab and Conshelf first sparked academic interest in sea bases. As it was modified and improved over the years, Hydrolab went on to house several hundred scientist-aquanauts over the course of many missions run through the mid-‘80s, in the waters off Bermuda and St. Croix in the U.S. Virgin Islands. NOAA’s ownership of the lab probably saved it from tanking—some privately-financed habitats of the era did not fare as well, like Aegir, another American-built sea dwelling.

Named for the Norse god of the sea, Aegir was the centerpiece of a marine research center in Hawaii and was tested to depths of more than five hundred feet. It had the look of a craft out of Star Wars, with a matching pair of cylindrical chambers laid end to end and connected by a ten-foot spheroid diving station reminiscent of Darth Vader’s escape pod. That structure was mounted on a platform and flanked, pontoon-like, by two slimmer cylinders—part of an innovative buoyancy control system that gave Aegir a mobile edge over habitats like Sealab, which had to be lowered to the seabed by crane. Once towed out to a site, Aegir could submerge and surface with the ease of a submarine, another sign of progress in habitat design. But by early 1973, a few months before NASA launched the first U.S. space station, the Aegir operation went belly-up.

So a project named for a god couldn’t make it, and yet one called La Chalupa—a name that roughly translates from Spanish as “boat with a tendency to capsize”—became one of the most successful of the era, largely thanks to a contract with the Puerto Rican government. Built by the private Marine Resources Development Foundation, this one looked like a barge on the outside, 50 feet long and 20 feet wide, but contained two interconnected tank-like chambers as living quarters inside.

Like Aegir, La Chalupa had the benefit of buoyancy control and greater ease of mobility. Bill Todd, NASA’s current project director of NEEMO, which runs astronaut training missions at Aquarius, calls La Chalupa’s design “brilliant,” even by today’s standards. It was built to accommodate crews of five for up to a month and could be placed at depths down to a hundred feet. La Chalupa was the base for a series of a dozen productive missions, at several locations around Puerto Rico, through the mid-1970s. Then the Puerto Rican funding ran out, and there seemed to be no other takers. After being brought back to Florida, where it had been built, La Chalupa languished for a decade but was finally converted into Jules’ Undersea Lodge, still the world’s only underwater hotel, which sits in about 30 feet of water in a Key Largo lagoon—shallow enough so that scant decompression is required, but its guests still get a taste of the life aquatic.

The Murky Future

There was a moment, around the late 1970s, when it looked as though the U.S. might finally get serious about its manned underwater activities. Some backers of marine science and exploration were even talking about the prospect of a “wet NASA”—an independent agency that could put the kind of money and energy into manned undersea missions that NASA put into human space flight. In the early 1980s, with the space shuttle program well under way—at an estimated cost of at least $450 million per mission—the U.S. considered building Oceanlab, a kind of mobile habitat capable of delivering aquanauts to depths of a thousand feet. It sounded almost like a real-life version of the Nautilus from 20,000 Leagues Under the Sea—but without the pipe organ, library and a few other of Captain Nemo’s interior flourishes. Despite a show of enthusiasm from scientists, a price tag of at least $25 million was deemed too high in those budget-slashing years, and the plans for Oceanlab were scrapped.

Instead, after Hydrolab was retired in the ‘80s, NOAA had a new, state-of-the-art habitat built. That became the Aquarius. In 1988, from its construction site in Texas, Aquarius went to St. Croix to replace Hydrolab at a depth of about 50 feet. Four years later, it was moved to its current location in the Florida Keys National Marine Sanctuary, giving scientists access to the biodiversity of the third-largest living coral barrier reef system in the world.

Yet, for all its value, the government has decided that the minuscule $2.5 million or so a year it spends on Aquarius is just too much.


Backers worry that this latest scientific mission, which ended July 21, could be its last. In case that funding does dry up, the nonprofit Aquarius Foundation has hurriedly been set up to try to keep the habitat going. The end of Aquarius could also be the end of an age of manned undersea exploration—an era that’s still just beginning.

Journalist Ben Hellwarth is the author of the new book SEALAB: America’s Forgotten Quest to Live and Work on the Ocean Floor.









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