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Saturation Diving: The Incredible World of Underwater Construction

It’s been three and a half weeks since you have seen the sun. The inky darkness is only broken by a few lights of the other workers welding together a gargantuan pipe. A few inches of steel and glass or thin rubber suit are the only things that separate you from a deadly, crushing void, and if there is an emergency, the ascent is more dangerous than any creature lurking in the deep. However, our insatiable need for oil and gas means work must continue twenty four hours a day to install this pipeline hundreds of meters below the surface. This is the life of a saturation diver. Today, crews of men and women will stay submerged for months at a time to build megaprojects far from the eyes of most of civilization in the murky depths of oceans and lakes.

Ancient Divers

However, humans have been diving long before technology advanced to allow for long term deep sea habitation. Free diving, sometimes called skin diving, is the practice of diving with no breathing apparatus, but instead using only divers’ ability to hold their breath for mind boggling amounts of time, often over five minutes. In ancient Greece, free divers would use stone or metal weights around their neck to speed their thirty meter descent to the seafloor where they would collect sea sponges, coral, or even salvage shipwrecks. In Japan, the tradition of women free diving for pearls dates back over 2000 years and into the present with the ama, or sea women, who continue this proud tradition today.

As technology advanced, civilizations across the globe made devices for humans to go down farther and stay down longer. Greek philosopher Aristotle was the first to describe the use of a diving bell to extend dive times. A diving bell uses simple physics to create pockets of air accessible to divers far below the surface of the water. For a wet bell, a large and heavy object, usually made of metal, would be hollowed out with an open bottom and space inside, thus shaped like a bell. This diving bell was lowered into the water where it sank to just short of the seafloor. As long as the bell stayed vertical, the air would not escape to the surface. This created a pocket of air on the inside, allowing divers to duck into the space to grab a few breaths of air before going back out to continue their dive all while staying well below the surface.

The first Dive Suits

This technology proliferated nearly every seafaring culture and was largely unchanged for several millennia. Divers across the globe continued to use a combination of these diving bells and their ability to hold their breath for incredibly long periods of time to complete their underwater tasks. In 1715, the first steps toward modern wetsuits were taken, although it would hardly be recognizable today. An English merchant by the name of John Lethbridge took a pressure tight oak barrel, not at all dissimilar from those used to make and store whiskey, and attached a small viewing window. The diver would stick their arms through two holes which were made watertight by putting leather cuffs around their upper arms. Bellows attached with a hose to a small hole in the barrel provided with some small amount of air circulation to prevent suffocation. The machine was said to be able to dive to depths of over twenty meters and could be used in thirty minute intervals. Despite looking like a mideval torture device, it was actually quite successful. It was used on multiple salvage operations and Lethbridge became exceedingly wealthy from the invention. There are records of the device being used as late as 1794.

Despite this niche invention, diving was still an arduous and dangerous profession that was limited to the very few who worked to hone their physical skills for those long dives holding their breath. That was all about to change as the industrial revolution started to modernize nearly every aspect of life. In 1869, French novelist Jules Verne released a subnautical work that was well ahead of its time. 20,000 Leagues Under The Sea depicted the intrepid Captain Nemo and his incredible underwater ship The Nautilus. On top of depicting modern submarines long before their proliferation, he also described how the crew had suits that allowed them to go hunting under the waves, making it one of the earliest depictions of more modern diving in literature. Science fiction quickly became science fact and dive suits were standard by the beginning of the 20th century.

The Dangers

All of this brings us back to modern saturation diving. Why is it that divers need to spend over a month under the waves? This is because of the way that the human body handles pressure changes. Water is heavy. Every liter of water weighs a kilogram and when objects are under water, all of the water above them exerts its weight on them. This effect is called hydrostatic pressure. Although hydrologists study this effect and the many others that water exhibits, it is generally considered one of the most difficult branches of science. A popular legend says that when Albert Einstein’s son told his father he was studying hydrology, the scientist who discovered general and special relativity proclaimed that his son’s field was harder than his. With that in mind, this definition is incredibly oversimplified. Divers have found that the deeper they dive, the greater the hydrostatic pressure becomes since there is more water above them to press downward. The human body has an amazing ability to cope with these pressure changes, but it needs time to naturally adapt to the different pressure environments. If a diver experiences a pressure change too quickly, several different conditions can occur and all of them are exceedingly dangerous.

The first of these is called barotrauma. This condition can occur if divers descend too quickly. The differences in pressure inside and outside of their bodies can cause cavities in the body such as ear drums, the sinus, and lungs to rupture. It can even occur in the heart causing a heart attack or the brain resulting in a stroke.

barotrauma effect
Barotrauma Effect. By prilfish, is licensed under CC-BY

Secondly, divers can suffer from nitrogen narcosis. This is only suffered on dives that go below 30 meters. Nitrogen in the brain mimics the effects of drunkenness including loss of coordination and poor decision making. These are not ideal side effects when the divers are dealing with delicate and life saving equipment in the hostile environment of the depths.

The last and most severe condition is decompression sickness, also called the bends. Like the previous ailment, this also is caused by the presence of nitrogen in the body. On the surface, 78% of air is composed of nitrogen, 21% oxygen, and the remaining percent being a hodgepodge of other gasses. Our bodies are well equipped to deal with nitrogen and it isn’t even a substantial issue as divers descend. However, if a diver ascends too quickly, the body isn’t able to process the nitrogen through the lungs quickly enough as the nitrogen expands with the lower pressure. This causes bubbles to form throughout the body. These bubbles can result in very serious damage to body tissues and nerves. In the most severe instances, divers can be permanently paralyzed or even die if these bubbles occur in the brain.

With these health concerns, divers must be extremely vigilant in their compliance with decompression protocols. These protocols have divers ascend in pressurized containers that slowly release the pressure over time to allow the lungs to process the nitrogen through their lungs naturally and return to standard atmospheric pressure. As a rule, for every 30 meters they descend, it takes a full day to decompress with one more full day added to assure worker safety. Considering that some of these missions dive to 300 meters below the waves requiring an 11 day decompression period, both companies and workers have found that it is much more efficient to have divers stay down at depth for a month at a time and only go through the lengthy decompression a few times a year.

Living in Murky Depths

Just as you would imagine, staying hundreds of meters below the waves for this duration begets a myriad of issues. The first of these is making a habitat that is safe for long term habitation. With little help available in an emergency, and an ascent to the surface just as deadly, the habitats must be overbuilt to minimize risk to the lowest possible probability. Just as humans suffer effects from the hydrostatic pressure of the water, the habitat does too. The larger the space is, the harder it is to support it from the rising pressure. This means that the majority of the rooms in the habitat aren’t much larger than a standard minivan. For example, the living quarters of a standard space for six divers has a footprint of about two meters wide and five and a half meters long. There are also very few portholes to look out of and they are rarely larger than ten centimeters across.

All that being said, there are a plethora of different habitats that are all made to the specifications and needs of the expeditions. Although some of these habitats are designed to stay at depth indefinitely, most of those are designed for long term research, are significantly larger, and don’t generally dive to depths below one hundred meters or so. These research habitats are often equipped with cutting edge technology and some even filter and recycle the internal atmosphere by replacing the carbon dioxide exhaled by the inhabitants with fresh oxygen generated by algae.

The vast majority of habitats don’t operate independently and have a support ship on the surface that supplies the divers with their daily needs. The support ship is responsible for cooking and providing their food, disposing their waste, and maintaining their tools and equipment. Cramped inside their miniscule accommodations, it would make these tasks rather difficult otherwise. These modular units tethered to the ship and are raised back inside at the end of the day’s work. The entire pod enters through a moon pool in the hull of the ship. Moon pools operate under the same principles as diving bells, leaving an opening into the ocean that can be accessed from inside the ship, though there are usually bay doors that can close the opening off. Despite the fact that the divers are no longer beneath the waves, they still must stay inside the pressurized container to avoid the effects of decompression. Any items that pass from the habitat and into the ship or vice versa are done so through pressurized air locks. Several of these pods operate concurrently, with one crew sleeping while the other delves back down to continue the work. This assures that projects can be continued constantly with no gap in productivity.

Luckily, although being trapped in a small metal tube with five other people for a month or more might not sound appealing, the divers are extremely well compensated for their time. The men and women who work on the support ship make an admirable $33 dollars an hour plus have accommodations and food covered during their excursions. That is $68k a year if they work standard forty hour work weeks. For the divers, the pay is considerably more. Starting salary is around $1,400 a day, and you are paid for each of the 28 days of your stent, including any decompression time. If you only worked four months out of the year, that would net you a cool $156,000 a year. If you shortened the intervals between dives to only the five week break required by law, that would increase significantly. That doesn’t even include bonuses for working particularly dangerous jobs or raises that you will inevitably receive as your skills and experience grows. Many of these experienced divers make over $300,000 while working only four months out of the year.

If extreme danger, cramped quarters, and long stents away from home seem worth the pay, you may be in luck because saturation diving is a growing field. As many parts of the world industrialize for the first time, there is an increased need to accommodate these growing metropolises with modern amenities and fuel the engines of progress. Since the majority of saturation divers are assembling pipelines for oil rigs or oil and gas transportation, this field isn’t likely to slow down until our consumption of fossil fuel does. Despite many attempts to lessen this and avoid the worst effects of climate change, it doesn’t seem like demand will be lessening any time soon.

If you want to enter this field, the first step is to become a certified commercial diver. That involves completing a course at one of the many certified dive schools across the globe. With a high school diploma or GED, you can generally get accepted into these programs without too much difficulty. The last step before your official certification is an additional 625 hours of instruction. Many divers get this certification and experience by joining the Navy and completing the training and hours with them. If you decide not to go with the military route, you would need to gain experience as a commercial diver. After several years honing your trade and making connections in the industry, then you could finally embark on an excursion to work as a saturation diver.


While researching this topic, there were several interesting details that we wanted to include, but didn’t quite fit nicely into any of the sections, so we’ve tacked them at the end here. Think of them as Mini Sideprojects on Megaprojects

It is no accident that the technology required for saturation diving mirrors that astronauts use to stay safe outside of Earth’s atmosphere. They are incredibly similar considering the remarkably different environments. In fact, all astronauts train in underwater environments to prepare them for the perils of extraterrestrial living. NASA has been using the Neutral Buoyancy Laboratory (NBL) at Johnson Space Center in Houston, Texas since 1995. Essentially a massive pool, the facility is sixty one meters long, thirty one meters long, and twelve meters deep. Full scale mockups of the space shuttles, the Hubble Telescope, the Spacex Dragon, and portions of the International Space Station, have been submerged here for astronauts to practice their missions. Underwater environments are good substitutes for the microgravity that astronauts will experience when conducting missions in space.

The 6.2 million gallon tank includes mock-ups of International Space Station modules and other training materials.
NBL The 6.2 million gallon tank includes mock-ups of International Space Station modules and other training materials. By NASA Goddard
Photo and Video, is licensed under CC-BY

When saturation diving first emerged in the 1960’s, many different technologies emerged to cope with the new and extreme circumstances faced by divers. One of the unsuspecting innovations came in the world of horology. It is critical that divers have accurate timepieces. When your life is linked to a tank with a limited supply of oxygen, it’s best not to leave timing to chance. However, divers going to these new terrific depths found an unexpected problem. The watches were shattering when divers resurfaced.

The Rolex watches were the tools of the trade for divers. Despite the privileged position of luxury that Rolex maintains today and had then, their watches first gained that status by being tools that surpassed anything else in the market. Needless to say, when divers emerged and found that their new Rolex had been obliterated despite being told by the manufacturer that it should survive those depths, they were displeased.

Engineers at Rolex were baffled by this at first. The watches had been tested under pressure numerous times and they had never failed in laboratory conditions. Even more confusing was that, upon closer inspection, the watches had exploded from the inside, not from the pressure of the waves above. They had to dive deeper to figure out where the issue lied. Rolex and Comex, a French diving company, worked together to try and discover the issue. Eventually, the culprit was discovered.

Divers that go down to the deepest depths have their tanks filled with a mix of helium and oxygen called heliox to help lessen the effects of the aforementioned decompression sickness. Aside from the hilarious side effect of having the divers sound like The Chipmunks upon surfacing, a separate side effect was that the miniscule helium molecules exhaled by the divers would seep into the watch through tiny spaces that the water molecules were too big to fit through. Then, as the divers neared the surface, the helium inside the case decompressed and exploded the watch from the inside. With the problem identified, the two companies worked together to create a helium escape valve. This small integrated device would allow helium to seep out of the device. A new watch with a helium escape valve was created.

You can still find this complication on many luxury watches today. The Rolex Seadweller, the Omega Seamaster Diver 300m, and the Tudor Pelagos are all modern luxury pieces that have this feature built in. However, essentially none of them are used for their intended purpose since saturation divers today use miniature dive computers to calculate their dive times and only wear dive watches as backups, or to honor the history of the profession. That leaves the other 99.9% of owners with a very expensive, and very useless feature.

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