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They Helped Foment a Dive Computing Revolution: RIP Cochran Undersea Technology (1986-2020)

Latin American distributor for Cochran Undersea Technology and certifiable dive geek Carlos Lander recounts the many firsts and innovations in dive computing created by microprocessor pioneer Mike J. Cochran (1941-2018). These included the first wireless air-integrated dive computer, automated sensors, hands free gas switching, tap interface, compartment-level conservation factors, what-if software, and the “Cochran Navy”—used to by the US Navy, to run their proprietary VVAL 18 algorithm.

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By Carlos E. Lander

Header image courtesy of C. Lander

Carlos Lander was the distributor for Latin America for Cochran Undersea Technology.

Michael James Cochran, genius and founder of Cochran Undersea Technology, revolutionized the design of dive computers (DCs) with the company’s state of the art US Navy Computer that impacted the entire DC industry. But before exploring the accomplishments of Cochran Undersea Technology, let’s answer an integral question:  “Who was Michael James Cochran?”

DEMA 2007. From left to Right: Larry Elsevier, Carlos Lander, Marty Heerschap and Mike Cochran.

Mike was born in Daytona Beach, Florida, on May 21, 1941. He worked on a missile tracking ship as a young adult but also had an illustrious career in electronics, receiving 57 patents, including ones for the microprocessor and microcomputer chip.1 The microcomputer chip patent was assigned to Texas Instruments (TI)—where Mike worked for many years—and issued to Gary Boon and Michael J. Cochran in July 1971.

For his work on that microcomputer chip, Mike won an IR-100 Award from Industrial Research Magazine (now known as R&D World Magazine). After he left TI, he worked with NASA and invented a DC for their astronaut training program. He founded Cochran Undersea Technology in 1986, and began designing and manufacturing DCs for recreational, sport, commercial, and military diving applications.

In 2016, he was awarded the honorary position of Admiral in the Texas Navy, an accolade commending exceptional community service. In that same year, he won the New Orleans Grand Isle (NOGI) Award—frequently known as the Academy Award of Diving—which recognizes pioneers of the underwater world.

Michael J. Cochran

Sadly, Mike passed away on December 2, 2018, at the age of 77, leaving behind a lasting legacy of studies and research in electronics. Mike was always driven by passion—so much so that he worked until the end of his life, having never created a plan for Cochran Undersea Technology to continue without him.

The Cochran Undersea Technology employed brilliant and gifted people such as Martin Heerschap, designer and engineer for the Cochran closed circuit rebreather (CCR) and liaison to the US Navy throughout the Navy DC’s development. Sales manager and tech instructor Larry Elsevier was another who worked closely with Cochran clients including the US Navy and NATO. He passed away in 2014. There was also Jeff Loudan, physicist, mathematician, and software engineer; Stuart McNair, engineer; and John Corso, talented diver and the face of the company before Mike’s passing.  

Creating An Advanced Dive Computer

Everything started in 1991 when Cochran Consulting Inc—the parent company to Cochran Undersea Technology—filed a patent for an “advanced dive computer,” which was intended to become an Oceanic air integrated DC.2 While that specific product was never patented, Cochran’s DC led to a huge advancement in the field. First, Mike made a DC from a Single Board Computer (SBC), and then he programmed everything in an “assembly language,” securing very high-speed, real-time calculations on a reliable DC. 

An SBC refers to any computer that contains all of its components in one circuit board. This configuration is perfect for devices with limited hardware space, such as a DC. SBCs are self-contained and energy-efficient, important elements under diving conditions.

An assembly language is an architecture-specific, low-level programming language, and Mike used one to efficiently compile a very complex algorithm including a set of variables that, at the time, did not exist in a DC (breathing parameters being one).

NATO Exercise in Halifax by Doug Elsey.

The final product included a microprocessor, a depth and pressure transducer, an electrically conductive metal clasp, and other components that worked efficiently in a small package within a very low power consumption unit.

Consequently, Mike decided to produce his own line of DCs, dubbed Nemesis in the United States, and Aquanaut in the EU. Although the company worked with different brands, in the end they decided to concentrate on their own, the Cochran Dive Computer. No other manufacturer at the time designed and built every component of their DC in-house.

Cochran was the first company to produce a hoseless DC with the following design features:

  • Mike’s design allows the main computer to be attached to the tank, so all the information gathered by the pressure transducer is transmitted to a diver’s wrist monitor (a second computer) in real time3, including the diver’s breathing parameters and workload. The wrist unit could be used independently as a DC in the event of a tank unit failure. Other brands used a transmitter attached to the tank, limiting the amount of information that could be sent to the main unit in short data bursts.
  • As determined by Cochran, the cases on both units were air-filled (at 1 atm), ensuring that the cases were manufactured with material that was capable of withstanding extreme depths. Taking this approach required fewer case penetrations—such as buttons—and ensured an effective, long-term seal. In addition, the battery compartment was sealed from the electronics and built with materials that wouldn’t corrode. In an extremely rare case of flooding, the only damage would be to the battery compartment and not the electronics.
  • The case was equipped with three electrically conductive metal clasps instead of pushbuttons. Those stainless contacts, in conjunction with the electronics, could detect the difference between saltwater and freshwater and thus refine the depth calculation. They could also distinguish metallic objects and fingers via electroconductivity.
  • Another cool patented feature was the implementation of a vibration detector inside the unit which allowed the user to perform quick functions, like tapping the unit for five seconds to turn it on, or tapping it once to turn on the back light.
  • The Cochran computer accurately measured and recorded the altitude (pressure) every minute whether it was on or off, accounting for minute changes of nitrogen levels in tissue.4 
  • Other contemporary DCs accounted for changes in decompression conservatism, and while some commercially available computers offered conservatism customizations, they didn’t provide adjustment calculation guidance. The majority of DCs based the conservatism factor in changing altitude; instead, Cochran used gas-loading to add conservatism in proportional increments so that divers both understood and controlled their conservatism.
  • Cochran’s DC’s tandem PC software featured two capabilities not offered by any other manufacturer at the time. First, the PC software ran the same algorithm as the DC, behaving exactly as the DC did on a dive. Divers could perform a trial run on the PC graphically or review an existing profile. Secondly, divers could transfer gas loading and altitude characteristics from one DC unit into another DC unit. For example, if one computer malfunctioned, information would transfer from one unit to another. Therefore, divers could continue to dive with the new computer without noticing any difference.

  • Perhaps most importantly, the Cochran DC never locked a diver out; most DCs would block access for 24 hours if the diver violated a stop. Cochran’s DC allowed them to continue their dive, and the DC would continue off-gassing at their current depth. 

The Proprietary Cochran algorithm

Mike exchanged ideas with dive experts while developing Cochran’s proprietary algorithm, including Dr. Bill Stone, Dr. RW Bill Hamilton, and Capt. Edward Thalmann of the US Navy. He designed the circuit board with the algorithm in mind. During this period, Capt. Thalmann was developing the Navy’s proprietary VVAL18 algorithm with the intention of using it in a forthcoming Navy DC. His plan was to be able to test the DC on the manned test-dive data to evaluate its performance against the algorithm. 

Once Cochran Undersea Technology was awarded the contract to build the Navy DC, they had access to all the scientific studies, probabilistic software, and anecdotal data on the installation of VVAL18 into a DC, which was pivotal to the development of Cochran’s own decompression algorithm. Cochran’s algorithm for the Nemesis included compensation for a bubble formation, and the Gemini—based on the Nemesis prototype—added variables for ascent rate and breathing parameters. The algorithm is based on a modification of Haldane’s decompression model, with compartments between five and 480 minutes.

HS2011-P004-005 29 Sept 2011 Halifax, Nova Scotia. The Fleet Diving Unit (Atlantic) (FDU((A)) hosts this years Deep Dive Exercise 2011, with four different locations at various depths looking for different items, an international exercise for divers from six different navies. There is a team from Norway, Finland, Portugal, Belgium, Canada, and USA. The aim of this exercise is to get all the divers from different countries to work together and to reach a depth, which is very uncommon for the casual or recreational diver. They use very specific equipment to dive to depths of 80 Meters, around 270 Feet. ©DND IMAGING 2011 Photo by Master Corporal (MCpl) Peter Reed, Formation Imaging Services, CFB Halifax, Nova Scotia.

There were several versions of the Cochran algorithm: 14, 16, and 20 compartment models. In the case of the 20 compartment version, the algorithm included fast compartments to compensate for helium gas and added a compensation for microbubbles related to ascent rate velocity. The model also used the same linear off-gassing from the Thalmann algorithm but included more than the fast compartment and ascent velocity to compensate for the aforementioned microbubble formations.

DC algorithm evaluation has been the subject of some research. For example, Dr. Carl Edmonds compared DC responses to a series of bounce dives. Dr. Karl E. Huggins used the same technique to evaluate DC algorithms by testing them on profiles that had known human subject results.



In his article published in 2004, Huggins notes that DC manufacturers did not validate their algorithms with human subject tests, so running a DC against a battery of previously tested dive profiles provided some rudimentary level of validation. So, when it came to validating their algorithm for use in both the Nemesis and Navy DCs, Cochran had the advantage of accessing the Navy’s database of man-tested dives.

Along with validation against the Navy’s database, the Cochran DC was validated against NOAA’s custom tables on the wreck of the USS Monitor, and the tables and DC were said to have matched well throughout the project.

In a 1989 Undersea and Hyperbaric Medical Society (UHMS) Workshop on Validation of Decompression Tables, UHMS determined that decompression algorithm validity could only be proven using primary data, such as results derived from controlled laboratory conditions. However, secondary data such as anecdotal performance reports could be cited as an operational evaluation but wouldn’t be considered proof of validity. 

Cochran’s Navy DC and what made it so special

In 1996, there were no commercial DCs running the VVAL18 decompression algorithm. The US Navy Experimental Diving Unit (NEDU) sought a manufacturer to install the VVAL18 on a DC following their specifications, which were far from simple.

Gary Gilligan (L) and Joel Silverstein (right) waiting to roll onto the USS Monitor to set the mooring line. All divers are using the new Cochran EMC-20H for practical beta testing. The computers had not been released to the market yet, and these dives would confirm field use. Photograph courtesy Silverstein-Weydig Archives.

Cochran won the bid (being the only DC designer and manufacturer entirely in-house likely had much to do with it) and delivered five modified Commander DCs with the VVAL18 algorithm, which they called “Cochran Navy.” After a few modifications, Cochran developed additions to the Single Board Computer (SBC) that allowed for massive dive profiling memory and a one-second sample diving profile (the Navy required a maximum of two seconds). The finished product was a DC that handled large amounts of data and self-test diagnostics.

Due to the breathing parameters, the DC would operate with air if the depths were shallower than 23 m/75 ft, or at PPO2 = 0.7 (MK16 MOD 0 UBA) at further depths. Additionally, hands-free Gas Switching was implemented to eliminate the need for buttons5. Part of the computational power was required for this, as the switch function would depend on depth and time. Also, the DC was programmable on the surface or via PC.

The device computed decompression properly whether the diver was below or above the stipulated stop. The residual gas was based on the diver’s depth: a real-time-calculator, without gimmicks. Therefore, the DC never shut down or left the diver hanging. Other advances were handling of the magnetic signature, EMF emissions, and visible light emissions (red light) required for Explosive Ordnance Disposal (EOD) work, and for stealth. The DC could be programmed for the needs of the mission with the Navy’s Analyst computer software.

According to probabilistic decompression models for the profiles tested on the Cochran Navy DC, the average risk predicted of decompression sickness occurrence was low: less than 1%, as expected. Therefore, the DCs were validated by faithful replication of the decompression schedules when exposed to simulated manned tested-dives.

In Conclusion

The last remaining stock of DC from John Corso.

The computers made by Cochran Undersea Technology,  while advanced for their time, were misunderstood and misused by many. Still, I consider Cochran’s Gemini DC the best ever made. If you’re not breathing from the back-gas and can reach certain pre-programmed depths, the computer automatically knows that you’re breathing from the deco bottle. If you start breathing from the back-gas again, automatically switching back without needing to push any buttons is an astounding characteristic unmatched by any other DC.

Unfortunately, the absence of a marketing division in the company gave Cochran the reputation of producing a military-only DC. The EMC-20H, a later DC, was also very advanced for its time, so it was sad to see Cochran vanish. I am comforted by the fact that I still have a few Cochran DCs I can use, and that they will serve me for many years to come.

I want to thank Martin and John for our conversations, and for their help in getting the facts straight.

Footnotes:

  1. Patent No. 4074351
  2. Patent Nos. US4949072, 4999606
  3. Transmitting information every second reduces noise; the power transmitter and a 250 kilohertz frequency results in a strong communication between units and protection from interference with other devices such as camera strobes and scooter motors.
  4. When a diver changes from a lower altitude to a higher one, the computer detects this change and adds nitrogen to the tissue compartments. The differential pressure between the nitrogen in the body and the higher altitude must be equalized (outgassed). Conversely, when a diver changes from a higher altitude to a lower one, the computer detects this change and removes nitrogen from the tissue. The computer automatically reacts to long-term stays at a constant altitude. If a dive is made while at altitude (whether the computer has already automatically reacted or not), the nitrogen algorithm within the Dive Computer is adjusted depending on the exact depth.
  5. Patent No. 5794616

Additional Resources

Cochran Undersea Technology Technical Papers:

Technical Publications (Various issues re: Cochran dive computers)

Task Loading, April 2013

Stealthy Diving, April 2013

Batteries Caveat Emptor, April 2013

Batteries: Disposable vs Rechargeable, April 2013

Environmental Concerns, May 2013

Cochran Dive Computer Firsts, September, 2017 


Carlos LanderI’m a father, a husband, and a diver. I’m a self-taught amateur archaeologist, programmer, and statistician. I think that the amateur has a different mind set than the professional and that this mindset can provide an advantage in the field. I studied economics at university. My website is Dive Immersion.  You can sign up for my newsletter here.

DCS

The SOS Automatic Decompression Meter: Bend-O-Matic or Game Changer?

Introduced in 1959, the Italian SOS Deco Meter—the forerunner of modern dive computers—was the first decompression device used by sports divers that automatically tracked users’ dive profiles. Here former French mine clearance diver, instructor, and historian Stephane Eyme takes us on a deep dive into SOS’s analog technology, compares its decompression prescriptions with those of the US Navy and French air diving tables for single and repetitive dives, and offers his perspective on its impact on the market.

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Text by Stephane Eyme. Photos and illustrations courtesy of Stephane Eyme. This story was first published on vintagescubadiving.com.

SOS Automatic Decompression Meter was the first mechanical analog dive computer.

Victor Aldo De Sanctis

The SOS Automatic Decompression Meter (“DeComPressimetro,” or DCP) was introduced in 1959 by Italians Victor Aldo De Sanctis—a known U/W cinematographer at the time—and engineer Carlo Alinari, both co-founders of Strumenti Ottici Subacquei (SOS), a Torino, Italy-based company specializing in scuba diving instrumentation.

DCP provided a decompression profile to scuba divers during an actual dive.

The device was very simply manufactured. It consisted of a waterproof deformable chamber filled with gas connected to a smaller, rigid chamber through a semi-porous ceramic cartridge. 

The rigid chamber was equipped with a bourdon tube to measure the inside pressure. A calibrated indicator interpreted these data to provide divers with a decompression status. The whole mechanism was enclosed in a metal and plastic housing.

Straightforward dive operation mode

During the dive:

Ascent and deco stops:

Quite a hit!

The device was distributed by SOS itself and many notable dive equipment companies. Throughout the US and Europe, Scubapro, Healthway, Beuchat, Sporasub, Nemrod, Barakuda and others, all sold the DCP at some point until the 1970s.

And so, the SOS DCP became the first successful decompression instrument sold at large scale to divers around the world. Scripps Institution of Oceanography reported more than 50,000 units sold.

A mind-blowing concept?

When the SOS DCP came out, the diving world already knew quite a bit about the decompression process. 

J.C. Haldane published his perfusion parallel compartments model in 1908, and a boom in decompression research followed..

We knew that human body tissues became saturated from a few minutes to several hours depending on the tissue, that saturation followed a logarithmic curve, and that it was symmetric with the desaturation process. 

We knew supersaturation ratios decreased linearly with increased ambient pressure (M-values), and that they were different for each compartment. 

Based on this knowledge, divers created and used several sets of deco diving tables, for example; US Navy 1956 and the GERS 65.

While it was true that , the diving community had long been aware that decompression was complex and had to account for a wide variety of factors,even with all those considerations, deco tables remained an approximation—a model that would probably differ slightly from diver to diver.

Still, some questions were bothering me

How could an engineer and a famous U/W photographer imagine a system like the DCP?

And, once they settled on the concept, how did they nail the exact piece of ceramic that rendered the entire human body a piece of clay?

And, furthermore, why did we trust them with our lives?

Below is an extract of the SOS DCP user manual. The device is compared to an “electronic brain.” Remember, this was in the sixties, and this “electronic brain” was at the forefront of technology!

I would have thought that, if SOS’s DCP manual was unmistakably indicating—in 1959—that the DCP was extrapolating decompression data from a piece of ceramic, lots of divers would have said, “WHAT?!” and kept using the dive tables. But then, in 1966, Scubapro essentially said the same in its DCP’s user manual, and still sold countless models!

“The mechanism is a pressure-sensitive sealed bourdon tube in a sealed chamber. The only passageway into and out of the sealed chamber is through a porous ceramic element. The element precisely controls the flow of gas into and out of the chamber. 

The gas is contained in a collapsible plastic bag which is protected by the stainless-steel case. An ambient pressure entry port and the strap slots allow for transmission of pressure to the collapsible bag. This differential forces the gas through the flow-controlling porous ceramic element into the sealed chamber. 

As the pressure builds up within the sealed chamber, the Bourdon tube response causes the indicating needle to move in a clockwise direction. This movement simulates the nitrogen absorption by the diver’s tissues. Upon ascending, the process is reversed.”

(Scubapro’s DCP Manual user 1966)

The results are here

On the other hand, and very surprisingly, DCP deco procedure profiles were not too terrible. On the first dive of the day, they actually weren’t too far from the profiles given by GERS65 or the NAVY56 table.

The GERS (Groupe d’Études et de Recherche Sous-marine) was created in April, 1945, by Cousteau, Tailliez, and Dumas. GERS was a unit of the French Navy in charge of clearing harbors and coast waters of WWII mines.

In 1965, the GERS expanded its previous dive table span from 45 m/147 ft to 85 m/277 ft. These tables were calculated on a Haldanian model with three and four tissues. They also considered two sets of constant supersaturation coefficients throughout the ascent.

Almost every diver in France until 1990 used these tables. They were the “official dive tables” of the French Federation for recreational diving.

The French Navy conducted a statistical evaluation of the safety of the GERS65 tables between 1966 and 1987, using human guinea pigs—err, young, fit, trained, and monitored military divers—and reported a not-insignificant number of accidents following the deco procedures indicated. This was one of a few other motivators for the Navy’s production of new tables—MN90.

I’ll use the GERS65 as a reference alongside the US NAVY56 table to evaluate the DCP deco profiles.

What happened on the first dive?

The following table compares DCP, NAVY56, and GERS65. The time indicated is the maximum bottom time allowed in minutes with no decompression stop on the first dive. GERS65 comes in meters only, rounded to the next meter depth to translate to feet.

(Scripps Institution of Oceanography, La Jolla)

Even if the concept of the SOS DCP is really mind-blowing, the results actually are not too far from the tables available at that time.

Looking more closely, DCP was, in fact, more conservative than NAVY56 and GERS65 up to 18 m/60 ft. It was pretty much the same as NAVY56 from 18 m/60 ft to 28 m/90 feet. Less conservative than the NAVY56, but still more conservative than GERS65 from 28 m/90 ft to 37 m/120 ft. Clearly less conservative than both tables after 37 m/120 ft—all for non-decompression dive profiles.

So, saying SOS DCP was not safe… Well, the maths don’t lie. Down to 28 m/90 ft, it was more safe than—or as safe as—the US NAVY56 tables during the first dive. The same happens with GERS65 down to 37 m/120 ft.

It is noticeable during deep dives—37 m/120 ft+—that the DCP became much less conservative than the two other tables. That might be an indicator that the DCP was well-calibrated for long compartments (and long, shallow dives) but not as well-calibrated for quick/medium ones (short, deep dives).

What happened on repetitive dives?

The time indicates the bottom time allowed with no Deco Stop on a consecutive dive.

I won’t get into too many details—I would need much more data to do the experiment justice—but the situation on a consecutive dive is a bit different than on a single dive. 

The DCP’s deco profile is almost always located between NAVY56 and GERS65. This means we almost never encounter the situation where DCP is safer than NAVY56. It seems to be less conservative than on the previous first dive scenario for non-deco dive profiles, but it is still safer than GERS65 in any case.

In short, DCP is safer than, or very comparable to, the US NAVY tables for a single ND dive down to 28 m/90 ft. During repetitive dives, DCP is almost always less conservative than NAVY56. It still remains safer than GERS65 in any dive down to 37 m/120 ft.

This is possibly why the manufacturer introduced the recommendation to make a deco stop for at least 5 minutes at 3 m/10 ft when diving to more than 45 m/150 ft. This seems a bit like a patch, doesn’t it?

Divers also applied other tricks for repetitive dives: “Move the safe-to-come-up point two ticks to the left for each dive that day.” Of course, the manufacturer did not indicate this rule in its user manual.

Different opinions about the DCP

Amazingly, it is difficult to clearly assess how good or bad the DCP was.

On one hand,

The very device looks like the result of a large experimental attempt to provide safe deco indications. It is not a scientific application based on multi-compartment Haldanian theory.

But DCP forgets serious deco parameters

SOS didn’t consider a few very serious parameters. Not even mentioned, for instance, was water temperature’s impact on deco schedules. Moreover, it approached the problem the wrong way—as cold water increased the viscosity of the gas in the deformable chamber, it diffused slower into the rigid chamber, incorrectly—and hazardously—giving the diver more no-deco bottom time.

Deco surface should differ according to air temperature for the same reasons. Divers sometimes used this factor to decrease surface time by setting the DCP close to the cooling fan of the air compressor!

In addition, different DCPs recommended considerably conflicting decompression schedules for dives with identical depth and time factors. Thus, the DCP’s no-deco limits given by the single dive table fluctuates—sometimes up to seven minutes!

Finally, the DCP’s recommended decompression schedules, in some cases, were more conservative (time-wise) than corresponding US Navy tables. But, in others, the recommendations were far outside the limits of staging according to the tables. Now we know why.

There is no failure warning

The manufacturer provided zero warnings about DCP failure. One potential failure is a needle that does not move or doesn’t start in the blue area, which is easy to check at the beginning of the dive. Another is a malfunctioning device—the needle moved toward the deco-stop zone, but much too slowly.

Don’t forget, this is a mechanical device and, as such, it can’t be expected to be failure-free. But, you had no way to anticipate the problem aside from checking the device right before you dived. Or perhaps attaching it to a line, immersing it to 30 m/100 ft depth for 30 minutes, checking that the needle is about to enter the deco-stop zone, and then waiting six hours to erase its nitrogen memory. Not too practical indeed!

Hence, you could potentially be diving with a malfunctioning device without knowing it, effectively risking your life.

No deco time scheduling

Lastly, the device didn’t provide a time schedule at the deco stop. The DCP only showed that you need to stop, but didn’t tell you for how long. This complicates consumption schedules, which stipulated air. You could easily find yourself with 50 bars in the tank and, without knowing it, beginning a 30 minute deco-stop… breathe shallow!

Scientists say IT IS NOT SAFE!

Scientists conducted very significant studies far beyond what a simple diver like me can understand. Their conclusions included:

“The meter’s performance is compared with the US Navy’s no decompression limits. It is concluded that use of the meter by recreational divers should be discouraged.” S. Howard, H. Bradner, K. Schmitt, Scripps Institution of Oceanography, La Jolla, Calif. 92093, USA Medical and Biological Engineering, September 1976

“Certainly, these techniques will make diving more complex for ‘fools’—but anyone who dives to depths in excess of 30 m/100 ft and thinks all is rosy when following a DCM is a fool. Deep diving in a hostile environment requires careful planning and thoughtful techniques, and no mechanical mechanism exists which can always reliably predict decompression schedules for divers at various depths for variable periods.  Surely, it is safer to err conservatively and stick to the ‘deepest depth X longest time’ method. There are many ex-patients who can recommend this practice from personal experience with DCMs which failed.” Carl Edmonds, Automatic decompression meters. SPUMS J . 1973; 3: 9

On the other hand,

There is a cadre of probably tens—if not hundreds—of thousands of dives using the DCP with no decompression incidents at all [See companion story by Bret Gilliam]. A huge number of divers can testify to using this device for many years with no problem. I probably used mine on a couple hundred dives. I’m still here to tell the tale!

Why? Let’s travel back in time to the 60s—when sex was safe, and diving was dangerous…

Equipment was emerging

The scuba equipment industry was in a very embryonic stage. Double hose scuba regulators were introduced no more than 15 years earlier. The first prototype of Maurice Fenzy ABLJ was developed in 1961—so until then you were diving on your legs—and Georges Beuchat introduced its Tarzan wetsuit in 1963 and the Jet Fins in 1964. 

Equipment in the 60s was, indeed, still very much emerging and would take time to penetrate the market; as a result, there were diving mandates to be in good physical shape, and divers are fit. In comparison, today’s equipment is far easier to use and even, sometimes, gives us the false impression that diving doesn’t require good physical condition.

Another kind of diver

In the 60s, divers simply weren’t the same as they are today! Scuba diving was still quite new and enjoyed by a very limited number of divers. A lot of them were former Navy—they were trained divers, fit and very experienced. This is one of the reasons why almost all national diving federations used a military-like training plan for new divers in the beginning.

This is mainly because instructors were former Navy divers, and it was the only way they knew. The long swims, the hard training sessions, the 5 minutes lifting a weight belt over your head while paddling… It came from the Navy.

As a result, the profile of the average diver back in the 60s was probably much closer to the military divers who were using the GERS65 tables than it is today. I guess if today’s divers were using the SOS DCP instead of electronic dive computers, results would be far more disastrous.

A large number of dives were done across Europe in federal clubs, with depth limits based on certification levels.

Another consideration is the dive profile itself: SOS’s DCP deco profile, when used shallower than 28 m/90 ft, was safer than (or as safe as) the US NAVY tables. In federal clubs, we did most of our recreational dives in this range due to certification level limits. Consequently, DCP guided numerous club divers with no problematic decompression outcomes during dives to less than a 30 m/100 ft. 

What were the key benefits supporting its success?

The DCP was a piece of cake to operate. No need to understand the table, thoroughly plan your dive, or remember your deco parameters. It was freedom. You just had to follow the guide and enjoy the dive!

Even the DCP’s user guide was only a seven-page booklet, of which three were useless for operational purposes! With just a quick read, you could strap it on and dive right away. It was extremely intuitive.

The DCP was very practical for calculating desaturation during surface-time between consecutive dives. DCP was doing everything for you. No nitrogen factor to calculate, no additional minutes on bottom time. You just dived, and DCP would do the rest for you.

Most importantly, the DCP was following your dive profile! That was quite a revolution in a square-dive-profile-world. Suddenly, you could dive much longer by slowly ascending a cliff and get more time to enjoy the dive! That was a true difference compared to table-based diving (at least for multilevel dives).

Was the DCP a bendomatic, or a game changer?

I think it is fair to say that the SOS DCP was a game changer in this emerging scuba world. The DCP would eventually bring a new perspective to diving. It was a brilliant idea, though probably a bit incomplete on the development side. 

Yet, the device laid out a genius concept—that we could design a device to do the math for us and change the way we dive. This probably inspired equipment manufacturers to look into electronic dive computers, the very same ones that appeared on the market during the 80s, but this time with a far more advanced scientific basis.

See Companion story: Diving the SOS: A Practical Discussion by Bret Gilliam

Additional Resources

Eyme’s website offers a wealth of historical resources and tools and tips: VintageScubaDiving.com 

InDepth: Oh Deco, Oh Doppler, O’Dive: Assessing the World’s First Personal Deco Safety Tool by Michael Menduno


As a former clearance diver with the French Navy, Stephane Eyme’s scuba diving experience includes running his own dive centre in the Canary Islands, supervising underwater archaeological excavations, and working for the largest dive shop in Paris. He has more than 30 years’ experience as instructor for the French Scuba Diving Federation (FFESSM) and is a PADI Master Instructor in teaching status. He runs the website VintageScubaDiving.com and often organises vintage try-dive events and participates in vintage equipment gatherings to share his passion with the diving community. He lives in Valencia on the Spanish Mediterranean coast, and lives by a motto: “What matters is being under [water].”

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