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Why Do Divers Run Out Of Gas?

Not surprising, the answer is more complicated than simply, they neglected to look at their gauges. Here Aussie diving medical researcher and former editor of DAN’s Annual Diving Report, Peter Buzzacott dives into several deep datasets including DAN’s Incident Reporting System (DIRS) and nearly four decades of cave diving incident data, to tease out some insights on gas emergencies and get a handle on the risks. Don’t stop those S-drills!



by Peter Buzzacott

See companion story for a guestimate of the risk: What is the Risk of Running Out of Gas?

Next year it will be 30 years since I first learned to dive. At the time, I had no idea that diving would occupy such a large part of my life. I distinctly remember kneeling on the sandy bottom end of the Great Barrier Reef, sharing a regulator with my buddy, and seeing sunlight rippling down through crystal clear water. On one of these “confined water” dives we had to swim horizontally for 10 m/30 ft holding our regulators out of our mouths and blowing a steady stream of bubbles. This wasn’t as easy as it sounds and we had to ration our bubbles to make it the whole way. Then, on an open water dive, the instructor took turns holding us with one hand and gripping a rope with the other while we took a breath, took the second stage out of our mouths, and then went for the surface, breathing out all the way. Up, down, up, down, the instructor went, with each student—one at a time. 

Courtesy PADI Worldwide. Copyright 2021, used with permission.

Most of today’s recreational dive courses do not include buddy breathing, they teach gas sharing with an alternate air source (AAS). Even before COVID-19, the buddy breathing skill had disappeared from most recreational training programs. The controlled emergency swimming ascent (CESA) has also disappeared from some programs. 

When I became an instructor, I made many hundreds of these but, now that I think about it, I don’t recall ever seeing anyone actually make one for real after running out of gas. These days everyone dives with two second stage regulators. In technical diving, we even dive with at least two cylinders; so, I wonder, do technical divers run out of gas and, if they do, then why?

What Do The Experts Say?

Some years ago, I asked a panel of 27 diving experts a similar question regarding recreational divers in general.1 The panel consisted of nine diving/hyperbaric doctors who had treated hundreds of injured divers; nine expert dive guides, most of whom were instructors; and nine expert recreational divers who had dived all over the world and written hundreds of feature articles for dive magazines. 

At the time, I suspected divers mostly ran out of gas because they didn’t pay attention to their gauge. But, to my surprise, the experts suggested about 20 reasons, such as diving deeper than usual, diving in a current, not wanting to end the dive for their buddy, using a smaller tank than their buddy, being underweighted, and many others, all of which sounded plausible. 

I sent the whole list of potential causes back to the group and asked them to rank, in their opinion, the five most likely causes. Then I gave five points to everyone’s most likely potential cause, four points to the second most likely, and so on. I added up all of the points and then ranked all the causes according to the total score. Then I sent this ranked list back to the group for one last review and asked them to consider the “weight of opinion” from the group as a whole, and to reconsider their top five reasons. 

As an expert panel, the group moved toward consensus. Just as I’d suspected, failing to monitor the gauge was the number one proposed potential cause of running out of gas, followed by inexperience, overexertion, inadequate training, and poor dive planning. Other than perhaps an unexpected current or underweighting leading to overexertion, the proposed reasons leaned toward human factors rather than the other two types of factors in the classic diving injury causal triad—those being environmental factors and equipment factors (Figure 1).2,3,4

Figure 1: The classic diving injury causal factors triad 2,3,4

The process I’d followed to gather expert consensus of opinion is called a “Delphi” process, which was originally developed by International Business Machines Corporation (IBM) to make forecasts on matters about which there was considerable uncertainty i.e. where there is little data. Opinions aren’t solid evidence; however, they can point towards a direction worth investigating. 

Next, I visited Divers Alert Network(DAN) as an intern and worked on an analysis of diving fatalities within a subset of technical divers—cave divers. More on that later, but while there, I had the opportunity to examine a large dataset of recorded dives from Project Dive Exploration, headed by Drs. Richard Vann and Petar Denoble. 

The dataset we had at that time revealed over 50,000 dives recorded by more than 5,000 recreational divers, (including an unknown number of technical divers). We examined these data in two ways. First, to control for environmental and equipment factors, and to focus on demographic (or human) factors, we counted each diver just once and compared those divers who had reported running out of gas, (during any recorded dive in that dataset), with divers who had not run out of gas. Surprisingly (to me), having run out of gas was more common than expected among older females (males were more likely to report other problems, like rapid ascent). 

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Next, to control for the human factors, we looked at just the dives made by divers who had made both at least one dive where they ran out of gas, and at least one dive where they did not run out of gas. I wanted to know what it was about those dives that might have caused the divers to run out of gas. Well, it turned out the out-of-gas dives were deeper, shorter (probably because they were deeper), often made from a live-aboard or charter boat, and involved a higher perceived workload.5 Hmmm… Perhaps overexertion was a factor after all.

After returning to Western Australia to undertake a PhD researching this, I spent the next few years recording 1,000 recreational dive profiles made by 500 divers. I recorded their start and end pressures, tank size, and noted factors such as current, how they felt their workload was (resting/light, moderate, or severe/exhausting), how many dive experiences they had, and what previous dive training they had completed. For the analysis, dives made by divers who exited with <50 bar/725 psi of pressure (needle in the red zone, n=183) were compared with other dives recorded at the same time at the same dive site (n=510) by divers who exited with >50 bar/725 psi pressure remaining (needle not in the red zone). 

Ending a dive low on gas was correlated with younger males with a longer break since their last dive, fewer lifetime dives, at deeper depth, and a higher rate of gas consumption (adjusted to an equivalent surface air consumption (SAC) rate, for comparison between dives made at different depths). Perhaps more tellingly, compared with 1% of the dives with >50 bar/725 psi at the exit, 11% of the low-on-gas divers reported being surprised at the end of the dive by how low their remaining gas pressure was.6 A more detailed analysis of the average workload associated with recreational diving, using this same dataset, identified that higher perceived SAC rate was not associated with sex but was associated with older age, lower dive certification, fewer years of diving, higher perceived workload, and other factors.7 

Technically Out of Gas

Returning to the topic of technical diving, a colleague and I re-examined the DAN cave diving fatality reports collection that I had worked with as an intern, and this time we concentrated on the previous 30 years of data: 1985-2015. Dividing it into two equal halves which we referred to as the “early” and “late” groups, reading each report carefully, and using a reliable cave diving fatality factors flow-chart previously developed,5 we classified factors associated with each cave diving fatality and then compared the two groups. 

In the late (more recent) group, the proportion of cave divers who were trained in cave diving had significantly improved, perhaps due to increased awareness of the need for proper cave diver training before entering a flooded cave. The majority of the 67 trained cave divers in our dataset were diving with two cylinders on their back (doubles), and the late group was diving further into the cave than the early group. Of the 67 trained cave divers, 41 (62%) had run out of gas. Looking at the five “golden rules” of cave diving, the “rule of thirds” was the most common (n=20) rule that was suspected to have been broken by the trained cave divers: the most lethal.9

So, it would seem that some technical divers do run out of gas, though thankfully that appears rare. We should bear in mind that cave divers may differ from other types of technical divers in their procedures, demography, and equipment; their environment (by definition) certainly differs from that of wreck divers. 

Currently, I know of no ongoing research into out-of-gas incidents among technical divers, other than the current Diving Incident Reporting System, hosted by DAN. An analysis of the first 500 reported incidents recently examined every incident—recreational and/or technical—during which the diver ran out of gas.10 The sample (n=38) was divided into two groups: those who made a controlled ascent (e.g. on a buddy’s donated regulator) and those who made rapid ascent (e.g. a bolt to the surface). 

Among divers who reported having run out of gas, but survived to report the incident, 57% of the rapid ascents resulted in a reported injury. Among the 24 controlled ascents, just 29% reported an injury.10

Among divers who reported having run out of gas, but survived to report the incident, 57% of the rapid ascents resulted in a reported injury. Among the 24 controlled ascents, just 29% reported an injury.10 This modern finding is in line with the statistics reported 27 years ago by Dr. Chris Acott when he analyzed more than 1,000 diving incident reports. Examining 189 out-of-gas incident reports, Dr. Acott found 89 made a rapid ascent, and 58% of those reported an injury. Among the 79 controlled ascents, only 6% reported an injury.11 

Table 1 shows the total number of dive incidents in each category, after adding both studies together. It seems to me that, while we have moved on from buddy-breathing and the controlled emergency swimming ascent, in the last 30 years the problem of running out of gas has not gone away. 

No Injury
(row %)
(row %)
(col %)
Non-rapid ascent 91 (88)12 (12)103 (50)
Rapid ascent43 (42)60 (58)103 (50)
Total134 (65)72 (35)206 (100)
Table 1: Injuries among 206 out-of-gas dive incidents by ascent rate10,11

In conclusion, the evidence confirms what we all know: running out of gas is associated with diving injuries and fatalities. It appears that the level of correlation of demography information (like age and sex) with out-of-gas incidents may depend upon the study design, the pool of divers studied, and/or the specific potential causes of running out of gas being investigated. For example, in one study, older females were more likely to self-report out of gas problems; in another study, young males’ remaining gas was measured and observed to be low. In yet another study, SAC rate increased when perceived workload increased, regardless of sex. 

Therefore, I’d suggest it is prudent to consider everyone potentially at risk of running out of gas and, in order to mitigate this risk, both recreational and technical divers should be proficient in gas planning and monitoring their remaining gas, regardless of age and/or sex. 

[Ed.note—Most agencies today require some level of proficiency in managing emergency out of gas scenarios. For example, GUE requires divers at all levels to train regularly for this eventuality. This training also emphasizes gas management strategies like “minimum gas reserves” and the related “one third” rule to ensure divers always have enough supply to share gas aka buddy breathe from any point in the dive, and all the way to the surface. Violation of these strategies risks insufficient gas in all environments.]


The influence of workload is interesting, and technical divers who perceive an elevated workload may well remember that this has been associated with both higher rates of gas consumption and unexpectedly running low on gas. So, when detecting a current or perceiving an elevated workload, I recommend keeping a closer-than-usual eye on the remaining gas and, if a current is suspected before the dive, then plan for an elevated SAC rate. 

The influence of training/certification consistently appears to be associated with the risk of running out of gas, as does having made fewer lifetime dives. Highly trained and experienced divers might bear this in mind when diving with buddies who are newer to our sport. Offer them opportunities to gain experience and recommend additional training when they are ready. We were all inexperienced once.

Technology has improved in recent years; for example, tank pressure transponders are more reliable today than ever before. It is possible that in the future these resources, coupled with audible alarms, may prove to be highly effective at preventing technical divers from running out of gas. Until we know how effective such alarms are at preventing out-of-gas dives, our best course of action is to dive within the limits of our training and experience, and to keep an eye on our remaining gas. 

See companion story for an estimate of the risk: What is the Risk of Running Out of Gas?

Do you think that it could it happen to you?


1. Buzzacott P, Rosenberg M, Pikora T. Using a Delphi technique to rank potential causes of scuba diving incidents. Diving and Hyperbaric Medicine. 2009;39(1):29-32.

2. Edmonds, C. and Walker, D. Scuba diving fatalities in Australia and New Zealand: The human factor. SPUMS J. 1989;19(3): 94-104.

3. Edmonds, C. and Walker, D. Scuba diving fatalities in Australia and New Zealand: The environmental factor. SPUMS J. 1990;20(1): 2-4.

4. Edmonds, C. and Walker, D. Scuba diving fatalities in Australia and New Zealand: The equipment factor. SPUMS J. 1991;21(1): 2-5.

5. Buzzacott P, Denoble P, Dunford R, Vann R. Dive problems and risk factors for diving morbidity. Diving and Hyperbaric Medicine. 2009;39(4):205-9.

6. Buzzacott P, Rosenberg M, Heyworth J, Pikora T. Risk factors for running low on gas in recreational divers in Western Australia. Diving and Hyperbaric Medicine. 2011;41(2):85-9.

7. Buzzacott P, Pollock NW, Rosenberg M. Exercise intensity inferred from air consumption during recreational scuba diving. Diving and Hyperbaric Medicine. 2014;44(2):74-8.

8. Buzzacott P, Zeigler E, Denoble P, Vann R. American cave diving fatalities 1969-2007. International Journal of Aquatic Research and Education. 2009;3:162-77.

9. Potts L, Buzzacott P, Denoble P. Thirty years of American cave diving fatalities. Diving and Hyperbaric Medicine. 2016;46(3):150-4.

10. Buzzacott P, Bennett C, Denoble P, Gunderson J. The Diving Incident Reporting System. In: Denoble P, editor. DAN Annual Diving Report 2019 Edition: A Report on 2017 Diving Fatalities, Injuries, and Incidents. Durham (NC): Divers Alert Network; 2020. p. 49-67.

11. Acott C. Diving incidents – Errors divers make. Safe Limits: An international dive symposium; 1994; Cairns: Division of Workplace Health and Safety.

12. Buzzacott P, Schiller D, Crain J, Denoble PJ. (2018). Epidemiology of morbidity and mortality in US and Canadian recreational scuba diving. Public Health 155: 62-68. 

13. Buzzacott P. (editor) (2016). DAN Annual Diving Report 2016 Edition: A report on 2014 data on diving fatalities, injuries, and incidents. Durham, NC, Divers Alert Network

14. Buzzacott P (editor) (2017). DAN Annual Diving Report 2017 Edition: A Report on 2015 Diving Fatalities, Injuries, and Incidents. Durham (NC), Divers Alert Network.

15. Buzzacott P and Denoble PJ. (editors) (2018). DAN Annual Diving Report 2018 Edition: A report on 2016 data on diving fatalities, injuries, and incidents. Durham, NC, Divers Alert Network

16. Denoble PJ. (editor) (2019). DAN Annual Diving Report 2019 Edition: A Report on 2017 Diving Fatalities, Injuries, and Incidents. Durham (NC), Divers Alert Network.

You can add a diving incident to the DAN database by name or anonymously here: Diving Incident Reporting System (DIRS).

Dr. Peter Buzzacott MPH, PhD, FUHM, is a former PADI Master Instructor and TDI Advanced Nitrox/Decompression Procedures instructor, having issued >500 diver certifications. Today he is an active cave diver, holding various advanced cave diver certifications including advanced (hypoxic) trimix diver, and he is gradually gaining experience with CCR diving. To finance this, he conducts research into diving injuries and decompression/bubble modeling at Curtin University in Perth, Western Australia.

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Diving Safety

Does The Sport Diving Community Learn from Accidents?

Do we learn from accidents as a diving culture and, as a result, take the actions, where needed, to improve divers’ safety? Though we might like to think that’s the case, the reality is more complicated as human factors coach Gareth Lock explains in some detail. Lock offers a broad six-point plan to help the community boost its learning chops. We gave him an A for effort. See what you think.




by Gareth Lock

Learning is the ability to observe and reflect on previous actions and behaviours, and then modify or change future behaviours or actions to either get a different result or to reinforce the current behaviours. It can be single-loop, whereby we only focus on the immediate actions and change those, e.g., provide metrics for buoyancy control during a training course, or double-loop where the underlying assumptions are questioned, e.g., are we teaching instructors how to teach buoyancy and trim correctly? The latter has a great impact but takes more time, and more importantly, requires a different perspective. Culture is the ‘way things are done around here’ and is made up of many different elements as shown in this image from Rob Long. Learning culture is a subset of a wider safety culture.

Regarding a safety culture, in 2022 I wrote a piece for InDEPTH, Can We Create A Safety Culture In Diving? Probably Not, Here’s Why,” about whether the diving industry could have a mature safety culture and concluded that it probably couldn’t happen for several reasons:

  • First, ‘safe’ means different things to different people, especially when we are operating in an inherently hazardous environment. Recreational, technical, cave, CCR and wreck diving all have different types and severities of hazards, and there are varying levels of perception and acceptance of risk. The ultimate realisation of risk, death, was only acknowledged in the last couple of years by a major training agency in their training materials. Yet it is something that can happen on ANY dive.
  • Second, given the loose training standards, multiple agencies, and instructors teaching for multiple agencies, there is a diffuse organisational influence across the industry which means it is hard to change the compliance-focus that is in place. From the outside looking in, there needs to be more evidence of leadership surrounding operational safety, as opposed to compliance-based safety e.g., ensuring that the standards are adhered to, even if the standards have conflicts or are not clear. This appears to be more acute when agencies have regional licensees who may not be active diving instructors and are focused on revenue generation and not the maintenance of skilled instructors. There is very little, if any, evidence that leadership skills, traits or behaviours are taught anywhere in the diving industry as part of the formal agency staff or professional development processes. This impacts what happens in terms of safety culture development.
  • Finally, the focus on standards and rules aligns with the lowest level of the recognised safety culture models – Pathological from Hudson. Rules and standards do not create safety. Rules facilitate the discussion around what is acceptably safe, but they rarely consider the context surrounding the activities at the sharp end, i.e., dive centres and diving instructors and how they manage their businesses. These are grey areas. There is a difference between ‘Work as Imagined’ and ‘Work as Done,’ and individual instructors and dive centre managers must both ‘complete the design’ because the manuals and guides are generic, and manage the tension between safety, financial pressures, and people (or other resources) to maintain a viable business. Fundamentally, people create safety not through the blind adherence to rules, but through developed knowledge and reflecting on their experiences, and then sharing that knowledge with others so that they, too, may learn and not have to make the same mistakes themselves.

The proceeding discussion brings us to the main topics of this article, does the diving industry have a learning culture, and what is needed to support that learning culture?

What is a learning culture?

In the context of ‘safe’ diving operations, a learning culture could be defined as “the willingness and the competence to draw the right conclusions from its safety information system, and the will to implement major reforms when their need is indicated.” (Reason, 1997). Here we have a problem! 


The industry is based around siloed operations: equipment manufacturers, training agencies, dive centres/operations, and individual instructors. Adopting a genuine learning approach means that the barriers must be broken down and conversations happen between and within the silos. This is very difficult because of the commercial pressures present. The consumer market is small, and there are many agencies and equipment manufacturers that are competing for the same divers and instructors. Also, agencies and manufacturers have competing goals. Agencies want to maximise the number of dive centres/instructors to generate revenue, and one of the ways of doing that is to maximise the number of courses available and courses that can be taught by individual instructors e.g., different types of CCR units. Manufacturers don’t want to realise the reputational risk because their equipment/CCR is involved in a fatal diving accident, but they also want to maximise their return on investment by making it available to multiple agencies and instructors. The higher-level bodies (WRSTC, RTC, and RESA) are made up of the agencies and manufacturers that will inherit the standards set, so there is a vested interest in not making too much change. Furthermore, in some cases, there is a unanimous voting requirement which means it is easy to veto something that impacts one particular agency but benefits many others.


This will be expanded in the section below relating to information systems as they are highly interdependent.

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What safety information systems do we have in the diving community?

Training agencies each have their own quality assurance/control/management systems, with varying levels of oversight. This oversight is determined by the questions they ask, the feedback they receive, and the actions they take. These are closed systems and based around compliance with the standards set by the agency – sometimes those standards are not available to be viewed by the students during or after their class! Research has been carried out on some of this quality data, but it appears to have focused on the wrong part e.g., in 2018, a paper was published by Shreeves at al, which looked at violations outside the training environment involving 122 diving fatalities. While the data would have been available, a corresponding research project involving fatalities inside the training environment was not completed (or if it was, it wasn’t published in the academic literature).

As the ex-head of Quality Control of a training agency, I would have been more interested in what happened inside my agency’s training operations than what occurred outside, not from a retributive perspective, but to understand how the systemic failures were occurring. I also understand that undertaking such research would mean it would be open for ‘legal discovery’, and likely lead to the organisation facing criticism if a punitive approach was taken rather than a restorative one.

Safety organisations like Divers Alert Network collect incident data, but their primary focus is on quantitative data (numbers and types of incidents), not narrative or qualitative data – it is the latter that helps learning because we can relate to it. The British Sub Aqua Club produce an annual report, but there is very limited analysis of the reported data, and there does not appear to be any attempt made to look at contributory or influential factors when categorising events. The report lists the events based on the most serious outcome and not on the factors which may have influenced or contributed to the event e.g., a serious DCI event could have been caused by rapid ascent, following an out-of-gas situation, preceded by a buddy separation, and inadequate planning. The learning is in the contributory factors, not in the outcome. In fairness, this is because the organizations do not have to undertake more detailed investigations, and because the information isn’t contained in the submitted reports.

Research from 2006 has shown that management in organisations often want quantitative data, whereas practitioners want narrative data about what happened, how it made sense, and what can be done to improve the situation. Statistical data in the diving domain regarding safety performance and the effectiveness of interventions e.g., changes to the number of fatalities or buoyancy issues is of poor quality and should not be relied upon to draw significant conclusions.

What is required to populate these systems?

There are several elements needed to support a safety information system.

  • Learning-focused ‘investigations’.
  • Competent ‘investigators’.
  • Confidential and collaborative information management and dissemination systems.
  • Social constructs that allow context-rich narratives to be told.

Learning-focused ‘investigations’. The diving industry does not have a structured or formal investigation or learning process, instead relying on law-enforcement and legal investigations. Consequently, investigations are not focused on learning, rather they are about attributing blame and non-compliance. As Sidney Dekker said, “you can learn or blame; you can’t do both”. The evidence that could be used to improve learning e.g., standards deviations, time pressures, adaptations, poor/inadequate rules, incompetence, and distractions… are the same elements of data that a prosecution would like to know about to hold people accountable. Rarely does the context come to the fore, and it is context that shapes the potential learning opportunities. “We cannot change the human condition, but we can change the conditions in which humans work.” (James Reason). Rather than asking ‘why did that happen’ or even ‘who was to blame’, we need to move to ‘how did it make sense to do what they did’. ‘Why’ asks for a justification of the status quo, ‘how’ looks at the behaviour and the context, not the individual.

Competent ‘investigators’. As there isn’t any training in the diving domain to undertake a learning-focused investigation, we shouldn’t be surprised that the investigations focus on the individual’s errant behaviour. Even those ‘investigations’ undertaken by bodies like DAN, the NSS-CDS Accident Committee or the BSAC do not involve individuals who have undertaken formal training in investigations processes or investigation tools. A comprehensive learning review is not quick, so who is going to pay for that? It is much easier to deflect the blame to an individual ‘at the sharp end’ than look further up the tree where systemic and cultural issues reside. The education process for learning-focused investigations starts with understanding human error and human factors. The Essentials class, 10-week programme, and face-to-face programmes provide this initial insight, but the uptake across the industry, at a leadership level, is almost non-existent. Four free workshops are planned for Rebreather Forum 4.0 to help address this.

Confidential information management system. Currently, no system allows the storage of context-rich diving incident data outside the law-enforcement or legal system in a manner that can be used for learning. After discussions with senior training agency staff, it appears that as little as possible is written down following an incident. When it is, it is shared with the attorney to enable the ‘attorney-client’ privilege to be invoked and protected from discovery. If internal communications occur via voice, then the potential learning is retained in the heads of those involved but will fade over time. Furthermore, if they leave that role or organisation, then the information is almost guaranteed to be lost.

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Social Constructs: Two interdependent elements are needed to support learning: psychological safety and a “Just Culture.” With the former, the majority of modern research strongly suggests that it is the presence of psychological safety that allows organisations to develop and learn (Edmondson, 1999). Edmondson describes numerous case studies where organisational and team performance was improved because incidents, problems, and near-misses were reported. Paradoxically, the more reports of failure, the greater the learning. It was not because the teams were incompetent; they wanted to share the learning and realised that they could get better faster with rapid feedback. They also knew that they wouldn’t be punished because psychological safety is about taking an interpersonal risk without fear of retribution or reprisal – this could be speaking up, it could be challenging the status quo, it could be saying “I don’t know”, or it could be about trying something new and coming up with an unexpected outcome.

The second requirement is a Just Culture which recognises that everyone is fallible, irrespective of experience, knowledge, and skills. This fallibility includes when rules are broken too, although sabotage and gross negligence (a legal term) are exceptions. Neither a Just Culture nor psychological safety are visible in the diving industry, although some pockets are present. To support psychological safety (proactive/prospective) and a Just Culture (reactive), there is a need for strong, demonstrable leadership:

  • Leaders who have integrity – they walk the talk.
  • Leaders who show vulnerability – talking about their own mistakes including the context and drivers; leaders who want to look at organisational issues inside their own organisation – not just point fingers at others problems.
  • Leaders who recognise that human error is only the starting point to understand something going wrong, not the end.

‘…the will to implement major reforms…’

This is probably the hardest part because learning involves change. Change is hard. It costs cognitive effort, time, and money, and this has an impact on commercial viability because of the need to generate new materials, to educate instructor trainers/instructors and divers about the change and do it in multiple languages. Unless there is a major external pressure, e.g., the insurance companies threaten to withdraw support, things are unlikely to change because there aren’t enough people dying in a single event to trigger an emotional response for change. For example, in the General Aviation sector in the US approximately 350 people die each year, but if these deaths happened in airliners, it would mean two to three crashes per year, and this would be considered unacceptable.

In 2022, more than 179 people died diving in the US. (personal communications with DAN)

The most radical changes happen when double-loop learning is applied.

NASA did not learn from the Challenger disaster because it focused on single-loop learning, and when Columbia was lost, the investigation unearthed a lack of organisational learning i.e., double-loop learning. Chapter 8 from the Columbia Accident Investigation Board provides many parallels with the diving industry. The recent changes to PADI drysuit training standards following a fatal dive on a training course provide an example of single-loop learning – fix the ‘broken instructor’ and clarify course training requirements. The double-loop learning approach would be to look at self-certification and the wider quality management across the agency/industry; however, such an approach has significant commercial disadvantages across the board.

Creating a Learning Culture

The previous paragraphs talk about many of the issues we’ve got, but how do we improve things?

  1. Move to using a language that is learning-based, not ‘knowing’-based. This video from Crista Vesel covers the topic relatively quickly. This includes not using counterfactuals (could have, should have, would have, failed to…) which are informed by hindsight bias. Fundamentally, counterfactuals tell a story that didn’t exist.
  1. Look to local rationality rather than judging others. Move from who (is to blame) and ‘why did you do that?’, to ‘how did it make sense for you to do that?’. Separate the individual from the actions/behaviours and stop applying the fundamental attribution bias where we believe the failure is due to an individual issue rather than the context.
  1. Look to break down the barriers between the silos and share information. Ultimately, the stakeholders within the diving community should be looking to create a safe diving environment. Throwing rocks and stones at each other for ‘incompetence’ is not going to help.
  1. Adopt the Five Principles of Human and Organisational Performance as outlined in this blog.
  1. Build ‘If Only…’ or something produced for the recreational market, into training programmes at the instructor trainer, instructor, and diver level. This way the culture can slowly change by telling context-rich stories that have ‘stickiness’. However, this requires a fundamental shift in terms of how stories are told and how risk is portrayed in the diving industry.
  1. Finally, recognise we are all fallible. Until we accept that all divers are fallible and are trying to do the best they can, with the knowledge they have, the money they have, the resources they have, the skills they’ve acquired, and the drivers and goals they are facing, then we are unlikely to move forward from where we are, and we’ll keep choosing the easy answer: ‘diver error’.


InDEPTH: Examining Early Technical Diving Deaths: The aquaCORPS Incident Reports (1992-1996) by Michael Menduno

InDEPTH: The Case for an Independent Investigation & Testing Laboratory by John Clarke

Gareth Lock has been involved in high-risk work since 1989. He spent 25 years in the Royal Air Force in a variety of front-line operational, research and development, and systems engineering roles which have given him a unique perspective. In 2005, he started his dive training with GUE and is now an advanced trimix diver (Tech 2) and JJ-CCR Normoxic trimix diver. In 2016, he formed The Human Diver with the goal of bringing his operational, human factors, and systems thinking to diving safety. Since then, he has trained more than 450 people face-to-face around the globe, taught nearly 2,000 people via online programmes, sold more than 4,000 copies of his book Under Pressure: Diving Deeper with Human Factors, and produced “If Only…,” a documentary about a fatal dive told through the lens of Human Factors and A Just Culture.

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