Saturation divers are professional deep-sea divers who work at extreme depths for extended periods, typically in support of offshore oil and gas operations (i.e., underwater welding, construction, maintenance, and repair).  

Saturation diving is a technique used for ambient pressure deep-sea diving, which allows sat-divers to stay at great depths (650 ft to 1,000ft or more) for extended periods.

The technique works by bringing all body tissues into equilibrium with the partial pressures of inert gases in breathing gaseous mixture and keeping them under constant pressure. 

A Look at the Dive Complexity 

Diving to such depths or just about any depth involves breathing pressurized air. Inert gases in it, such as nitrogen, dissolve benignly into your blood and tissues, as long as the weight of all the water above you keeps them compressed.  

But when you want to return to the surface, that gas needs time to diffuse out slowly. If not, if a diver shot straight to the surface, the gas would form bubbles, like in a shaken can of soda.  

Inside a diver’s body, it would be as if millions of tiny explosives began to detonate (one-by-one). Known as the bends or, more technically, decompression sickness, the condition can be catastrophically painful and debilitating, and, depending on the depth, nearly impossible to survive. 

Taking a 250-foot-hour dive would require a five-hour ascent to avoid getting even slightly bent. The condition (bends) was first seen in the 19th century, when men leaving pressurized caissons, used to dig tunnels and build bridges, mysteriously took ill and began dying. 

Below about 100 feet, divers breathing compressed air can develop what’s known as nitrogen narcosis, which does an excellent job of mimicking the feeling of being drunk.

The deeper you go, the drunker and more incapacitated you feel: Beyond 200 feet, you might become acutely disoriented, at 300 feet, you can black out. In addition, that amount of compressed oxygen becomes toxic to the human body. 

Around 1919, electronics engineer, and inventor Elihu Thompson figured that divers could avoid nitrogen narcosis by breathing a mixture of helium and oxygen.

In the following decades, a gas cocktail called heliox was developed, mostly helium, with sufficient oxygen and maybe a little nitrogen. 

Source: Mass Communication Specialist 2nd Class Fred Gray IV/ US Navy 

Image above shows the divers at the Navy Experimental Diving Unit prepare the Ocean Simulation Facility for a simulated dive to 500 feet. 

“It takes about 3.5 hours for an astronaut to make it back from space. Saturation divers have to decompress for days at a minimum.” 

Their Significance 

The world and, specifically, the Oil and Gas industry, these divers perform the delicate maneuvers required to put together, maintain, and disassemble offshore wells, rigs, and pipelines, everything from flipping flow valves, to tightening bolts with hydraulic jacks, to working in tight confines around a blowout preventer. 

With modern technologies, ROV (Remote Operated Vehicles) have been in play but they don’t have the touch, maneuverability, or judgment for the work/job as compared to a diver. 

Their work involves living in a pressurized environment for days or weeks, allowing them to perform tasks such as repairing pipelines, inspecting rigs, or installing equipment without needing frequent decompression stops. 

How the practice came into existence 

Experiments in the 1930s showed that, after a certain time at pressure, divers’ bodies become fully saturated with inert gas, and they can remain at that pressure indefinitely, provided they get one long decompression at the end.  

In 1964, naval aquanauts occupied the first Sea Lab—a metal-encased living quarters lowered to a depth of 192 feet. The aquanauts could move effortlessly between their pressurized underwater home and the surrounding water, and they demonstrated the enormous commercial potential of saturation diving. 

It soon became apparent that it would be easier and cheaper to monitor and support the divers if the pressurized living quarters weren’t themselves at the bottom of the sea. 

At this moment, all around the world, there are commercial divers living at pressure inside saturation systems (mostly on ships, occasionally on rigs or barges), and commuting to and from their jobsites in pressurized diving bells. They can each put in solid six-hour working days on the bottom. 

Saturation 

Layouts of these saturation systems differ from vessel to vessel, company to company, and field to field. Generally, the North Sea facilities tend to be slightly more accommodating, thanks to the strict regulations, but that’s not to say they are in any way spacious. 

Entering that first hatch puts the divers in a small round room known as the “wet pot”. It is used to transfer the divers to the diving bell through a hatch in its ceiling.

Through the wet pot, another hatch leads to the living space, where there is just enough room for four to six seats around a removable aluminum table and bed. 

In the bad old days, six guys would have to hot-bed three bunks, with one group working while the other slept. There are still ways to keep the work going 24/7.

On some vessels, up to four saturation chambers can be linked together through side hatches in the wet pots and connected by large metal hamster tubes. This enables multiple dive teams to be in constant rotation. 

Once the divers are tightly ensconced in the saturation chamber, the life support crew begins pumping in heliox, and the “blowdown” begins. The time it takes to get fully pressurized depends on the depth of the work site. 

“In essence, pressurization transforms the saturation chamber into a space in which the air around them, and filling their lungs and saturating their tissues, is exerting pressure equivalent to the weight of the water they will be working under.” 

Life Inside the Bell 

The divers are now saturated, and it’s the first job on the way; crews split into teams of two or three and alternate shifts. They are woken up an hour before they need to leave the ship. They eat and hydrate and use the bathroom (one quality that makes a good saturation diver is “the ability to shit on command.” Says Tweddle a sat. diver). 

They then put on a layer of their clothing, followed by their water-tight diving suits, which are equipped with circulating hot water systems to prevent hypothermia.

The dive team seals itself off in the wet pot and then, through the hatch in the ceiling, gets into a diving bell, at the same pressure as the chamber. Both spaces are sealed, and then they disconnect. 

The bell, shaped like an egg and about the size of a shower stall, is crammed with gauges, switches, communication equipment, and loops of hoses, referred to as umbilicals, that carry gas, electricity, voice communication, hot water, and video feeds back and forth between the divers’ helmets and the ship, via the bell. 

Once the bell detaches from the chamber, it is guided over to a moonpool, a hole in the boat’s hull, essentially, where it is lowered by cable to the working depth.  

One of the divers stays in the bell to monitor breathing, hot water, communication, and electrical systems. The other divers put on their dive helmets and depart to the bottom for six uninterrupted hours in the water.

During that time, urinating isn’t an issue, it’s one of the only jobs in the world where it is expected that you will pee in your pants. 

Divers carry minimal tools with them; everything else they need gets sent down directly from the ship—saws, torches, wrenches, welding equipment, collection bags. 

With such challenging and hard-working environments, it is thanks to these brave men that most homes stay warm and have power in Europe.