Diving Safety
Drift is Normal. Being a Deviant is Normal. Here’s Why
What causes individuals and organizations to drift from acceptable standards and behavior? Is it an aberration or something to expect, and what can we do about it? Human Factors coach Gareth Lock takes us for a deep dive into human biases and our tendency to drift, and what that means for human performance.


by Gareth Lock
Header image: a deviant diver on the SMS Cöln, and other pictures courtesy of Gareth Lock, unless noted
In 1994, two US Army Black Hawk helicopters were shot down by two US Air Force F-15 fighter jets over northern Iraq killing all 26 people on board the choppers. When the story hit the media, it was almost unbelievable that two highly professional aircrews being guided by other equally professional operators on the Airborne Warning and Control System (AWACS) aircraft could mistake the Black Hawk helicopters for Mil Mi-28 Hind helicopters. But they did!
In his excellent book Friendly Fire: The Accidental Shootdown of U.S. Black Hawks over Northern Iraq, Scott Snook developed and demonstrated the concept of practical drift, a theory whereby each sub-organisation or team has a certain amount of leeway to undertake their operations. This flexibility acknowledges that you can’t follow the rules exactly to the letter all the time. The problem is that these small deviations compound across the wider system with potential disastrous results; and, importantly, no one appears to recognize that the drift is occurring. Snook’s event map describes a complicated web of relationships between multiple stakeholders—the tasking organisation, the aircrew in the Black Hawks, the F-15 aircrew, and the AWACS control team—all of whom were doing the best they could with their limited resources and quickly changing circumstances.
Practical drift is similar to the “Normalization of Deviance,” a concept Diane Vaughan developed during her examination of the Challenger Shuttle disaster. Vaugn explored the idea in her 1996 book, The Challenger Launch Decision – Risky Technology, Culture, and Deviance at NASA. Normalization of deviance has been discussed in a number of recent diving blogs in an attempt to explore the acceptance of the (continued) breaking of a single rule.
Rather than focus on a single rule, we should consider Vaughan’s definition wider than the individual level, and look to a larger scale. “Social normalization of deviance means that people within the organisation become so accustomed to a deviation that they don’t consider it as deviant, despite the fact that they far exceed their own rules for elementary safety.” Neil Richardson, a safety and human factors professional (and colleague of mine) operating primarily in the aviation domain, offers another perspective while addressing the same point: “The Shuttle programme was risk-managed right up until the point it wasn’t and the Challenger and crew were lost.”
Risk management vs, uncertainty management
Risk management is often mentioned in the “professional” arm of diving and diver training courses—such as dive master, instructor, and instructor trainer courses—but it is rarely covered in detail during “user” courses or sport diving. Despite this lack of formal content and process, we are constantly managing relevant uncertainties with the goal of providing an enjoyable dive for ourselves and our students and reducing the likelihood of having an adverse event.
The term “uncertainties” has specifically been used instead of “risk” because of the way that we normally make decisions in an uncertain environment. When managing risk, we are often comparing historical analyses of quantitative data to determine likelihood and consequence using the logical or System 2 part of the brain. However, when we are managing uncertainties, we use a different part of the brain—often described as System 1—which relies on pattern matching, cognitive biases and mental shortcuts. Importantly, System 1 is heavily influenced by our emotions, which is why we often react quickly rather than logically.
Equating “risk” and “uncertainties” is like conflating the “apple” type of decision-making with the “orange” type of decision-making. They are both decision-making concepts, but they have different processes and applications and can lead to different outcomes.
We need to recognize that the uncertainties we deal with while diving aren’t just focused on physical safety/harm, but also cover legal, reputation, financial, psychological, and social uncertainties and their associated outcomes. Research has shown that the fear of psychological harm can be stronger than the fear of physical harm.
In the diving industry, when something goes wrong, the (social) media and “investigations” often focus on the proximal causes—those that are closest in time and space to the event—of what happened. There is a focus on violations, rule-breaking, human error, recklessness, or direct health issues, and only sometimes do supervisory/instructional factors come into the discussion. Furthermore, the media rarely examines “local rationality” (why it made sense for the individual to do what they did) or the immediate or wider organisational and cultural factors that may have been present.
Local rationality
If we focus on the local rationality to start with, we know that the majority of the time we are operating in System 1 mode, which is fast, intuitive, and pattern-matching based thinking. We are not actively paying attention to everything that we’re sensing; instead, we are picking what we think are the relevant or important factors based on our previous knowledge and experiences, focused by our present goals and expectations, and using those elements of information to make a decision.
Despite what some would think, you can’t pay 100% attention all the time! This means that we are literally ditching billions of bits of sensory data each day because, in real time, we don’t think those bits are relevant or important. When there are pressures that prevent us from being more thorough, we are trying to be as efficient as possible. These pressures might be related to time, money, peer-pressure, fear of failure, fear of non-compliance, or fixation on goals/outcomes. However, the more we get “right” without thinking about all of the incoming stimuli, the more we use this pattern to reinforce our decision and then repeat it. How often have you heard “We’ve always done it this way?”
Maybe an adverse event would provide a learning opportunity? Unfortunately, the likelihood of adverse events serving as cautionary tales is entirely dependent upon biases in our thinking and how those biases inform our interpretation of an event, adverse or otherwise. The following is a list of biases:
- Outcome bias describes the tendency to judge serious events more critically than minor events. This is because we disconnect the quality of the outcome from the quality of the decision. For example, those involved in a fatality with the same conditions as a non-fatality will be treated more critically; a poorly performing regulator that free-flows in 10 m/33 ft of cold water will be treated differently from the same regulator that free-flows in 40 m/131 ft of cold water because the consequences are more severe.
- Fundamental attribution bias is the tendency to attribute causality of an adverse event involving someone else to the individual involved rather than the situation or context. This is different to when we personally experience failure, as we often blame the situation or context! Inversely, when we personally experience success, we look at our skills and behaviors; but, when others succeed, we have a tendency to attribute the “opportunities” they had as the cause for success.
- Distancing through differencing is the tendency to discount failures in others as being relevant to ourselves because we are different to the other party in some way, even if the general conditions and context are the same. A recreational OC diver may forget part of their pre-dive sequence because they were distracted but an experienced OC technical diver may believe that they wouldn’t make that same mistake, even though the conditions were the same.
- Hindsight bias is the tendency to think that, if we had been in the adverse situation, we would have known at the time what the adverse event would have been and would have responded differently. Part of this is because we are able to join the dots looking backwards in time, recognising a pattern that wasn’t apparent in the moment.
Rewards
As a result of these biases, we aren’t very good at picking up small deviations in procedures because we experience “good enough” outcomes, and we are “rewarded” for gradual erosion of the safety margins that the original standards were created to address:
• We saved time (or weren’t late) as we skipped through the checks quickly.
• We saw more of the wreck or reef because we extended the bottom time and ate into our minimum gas margins.
• We managed to certify a few more students this month which helped pay the bills, even though we didn’t cover everything to the same level of detail that we normally do.
• We got some really great social media feedback because we took those divers somewhere they hadn’t been before—and shouldn’t have been either—but they loved it.

Rewards come in all sorts of shapes and sizes, but the common factor is the dopamine rush: Our brains are wired to favor the feel-good rush of a short-term gain over the prolonged reward of a long-term gain. On the other side of the coin, we are also willing to sacrifice a potential major loss in the future if there is a guaranteed minor loss now. For instance, imagine that you’re entering the water for the “dive of a lifetime” in cold water with a regulator setup that doesn’t breathe too well. You weren’t able to get it serviced because of time/money issues. At the end of this particular dive, you have to do a gas sharing ascent; someone else was out of gas due to an equipment failure, and both of your second stages freeflow and freeze, due to poor regulator performance, increased gas flow and the cold environmental conditions. This resulted in two people who were now out of gas and making a rapid ascent to the surface.
In hindsight, we can see where the failures occurred. But, in real time, the erosion of safety margins and subconscious acceptance of the increased “risk” are likely not considered. In mid-July 2021, I gave a presentation to Divers Alert Network Southern Africa (DAN SA) on the topic of setting and maintaining goals and how goal focus can reduce safety.
Organisations drift too
This article opens with the topic of normalization of deviation as it related to NASA and the Challenger Shuttle loss. The gradual, imperceptible shift from an original baseline through a series of “risk managed” processes and activities resulted in a “new” baseline that was far from acceptable when considering the original safety argument. This isn’t the first time an organisation has drifted, nor will it be the last.
Organisations are made of people, and there are reward systems in place within organisations which lead to a conflict between safety, workload, and financial viability. The image below from Jens Rasmussen shows this tension and the “safety margins” that are perceived to be in place. The difficulty is that we don’t know how big the gap is between the margin and catastrophe, so we keep pushing the boundaries until we get some feedback (failure) and hope that it isn’t catastrophic.
Another way of looking at this tension and drift is to use a framework from the Human and Organisation Performance (HOP) domain called the Organisational Drift Model from Sidney Dekker.
The premise here is that safety is “created” by the development of rules, processes, procedures, and a culture which supports adherence to these standards or expectations. In the modern safety domain, these rules, processes, and procedures are called “Work as Imagined” or “Work as Prescribed.” They rarely match exactly the operational environment to which they are going to be used. There are good reasons for that; you cannot document everything that you want your people (instructor trainers, instructors, dive masters, and divers) to do in every circumstance, so there will be gaps between what should be done and what is done. These gaps are filled in by experience and feedback. Some call this common sense, but you can’t develop common sense without personal experience!
As time progresses, there is an increased gap between the “Work as Imagined” (black line) and “Work as Done” (blue line). This gap is risk or uncertainty to the organisation. Not all drift is bad though, because innovation can come from drift as long as it is recognized, debriefed, and intentionally fed back into the system for improvement.

At the same time as individual and team performance is drifting, the operational environment is changing too. There are accumulations which are adding uncertainty/risk to the system: old or outdated equipment, external requirements changing, legislation changes, change of purpose of equipment or accommodation/infrastructure, and many others. Often these accumulations are dealt with by different people in an organisation, so the compounding effect is not seen.
The gap between “Work as Done” and the “Accumulations” line is known as capacity within the system. This capacity is managed by individuals, taking into account their experience, knowledge, skills, and attitudes towards and within the diving environment. Safety does not reside in paperwork, equipment, or individuals; it is created by those within the diving system taking into account all of the resources they have and the pressures they face while balancing workload, money, and safety dynamically.
However, when the capacity runs out (when the Work as Done line crosses the Accumulations line) an adverse event occurs. This event is now under the spotlight because it is obvious and cannot be hidden, especially if it is very serious. Hindsight clouds our ability to learn because we think the gaps must have been obvious. Effective organisational learning to prevent drift doesn’t need an adverse event. What it needs is a curious mind and the motivation to improve. If we stopped time 5 seconds before the lines crossed, while we still had capacity, then all of the learning opportunities would still be present and we could examine them. We would be able to see what accumulations are occurring, we would be able to see Work as Done actually was, and we would be able to increase the capacity of the system thereby reducing the likelihood of an adverse event. But that requires organisations to recognize that adverse events are outcomes from a complex system with many interactions, and where they set and demonstrate the acceptable standards and expectations. The absence of adverse events does not mean that you are operating a ‘safe’ system.
If drift is normal, what can I do about it?
First, recognize and acknowledge that drift exists. We all have a tendency to drift. If drift is occurring, look at the conditions that are causing the drift without focusing on the drifting individual themselves. This could be time pressures, financial pressures because of ‘cheap’ courses, lack of experience, high turnover of staff and low commitment to the sport by divers or dive professionals.
Secondly, create an environment where feedback, especially critical context rich feedback, is the norm. This has multiple benefits:
- Individuals find out where they are drifting from the standards/expectations which have been set.
- Organisations find out if their standards/expectations are fit for purpose and where issues about compliance are arising.
- Accumulations are identified in a timely manner and addressed.
There are a number of blogs on The Human Diver website and our Vimeo channel which help to develop a learning culture, understand how drift occurs via human error, and how to develop both a psychologically safe environment and a Just Culture. In terms of having an immediate effect, a post-dive/post-project debrief is one of the best methods, and you can download the DEBRIEF framework I created to help facilitate critical, learning-focused debriefs from here: www.thehumandiver.com/debrief
Remember, is it normal to err. It is what we do once we’ve made the error that matters when it comes to creating positive change in the future. If we focus on the individual and their behavior, things are unlikely to improve. However, if we look at the conditions and context, then we have the opportunity to reduce the chances of an adverse event in the future. And if we share those lessons, it isn’t just our organisation or team that improves, the diving community can too.
Dive Deeper
Be There or Be Deviant: HF In Diving Conference 24-25 September 2021

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 350 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. In September 2021, he will be opening the first ever Human Factors in Diving conference. His goal: to bring human factors practice and knowledge into the diving community to improve safety, performance, and enjoyment.
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Community
Why It’s Okay To Make Mistakes
To err is human. To trimix is divine? Instructor evaluator Guy Shockey examines the importance of learning through one’s mistakes, and most important, being willing to admit and share them with others, especially for those in leadership positions. It’s the only way to create ‘psychological safety” within our community and improve our collective diving safety and performance. Wouldn’t that be divine?

By Guy Shockey. Images by Andrea Petersen
A few months back, I read an article about a club where members talked about failure and making mistakes. This club required that members freely discuss their mistakes and failures without fear of judgment. The goal was to destigmatize failure and recognize that we learn by making the very mistakes we are afraid to talk about! Moreover, to become truly high performing and develop unique and creative solutions to problems, the article argued that we needed to be free of the worry of failing—to understand that “to err is human.”
The article went on to mention that for high performing teams to be successful, they needed to operate in an environment of “psychological safety.” This term was originally coined by Harvard professor Amy Edmondson, and Gareth Lock has written about the concept extensively. In his work with The Human Diver, Lock identifies psychological safety as a key component primarily missing in our diving culture. As a full-time diving professional and someone who delivers The Human Diver programs, I couldn’t help but reflect on the failure-destigmatizing club in the context of our diving culture in general and, more specifically, dive training.
Consider the humble Roomba robot vacuum cleaner. The Roomba learns how to clean a room by bumping into nearly everything in the room and, with some nifty software, creates a “map” of all the “vacuumable” space in the room. Then, it goes about its business efficiently and repetitively cleaning the room. The Roomba has learned by making multiple mistakes—much like humans do.
Now imagine being able to transfer that new “map” from one Roomba to another so a new Roomba doesn’t have to repeat the mistakes of the first as it sets out to vacuum the room. Finally, imagine this transfer of data to be less-than-perfect—perhaps, occasionally, the new Roomba will make some mistakes (from which it will learn). But it will make far fewer mistakes than the original Roomba had to make.
I’m sure you can see where I’m going with this. Humans learn the same way Roomba vacuums do (hopefully without running into as many hard surfaces), and we can transfer information between each other. Because the transfer process is less than perfect, we still make some of the same old mistakes. This is particularly interesting because, despite drawing specific and repeated attention to these common errors, students often still make the same errors! One of the most important parts of instructor training is educating future instructors to recognize where these common mistakes will occur and encouraging them to ramp up to being hyper-vigilant rather than regular-vigilant.

Learning Through Mistakes
One way we learn is by making mistakes, talking about them, and sharing the experience in the hopes that future divers don’t have to make the same ones. At its core, this is the very essence of learning. Incidentally, this is also what makes experience such an important characteristic of a good teacher. The more experience the educator has, the more mistakes they’ve made and, consequently, the more information they can transfer. Fear of owning our mistakes keeps us from learning from them; perhaps more importantly, it means that others will miss out on these important lessons.
Yet, in diving culture, we (for the most part) shy away from discussing the mistakes and errors we (hopefully) learned from for fear of being considered a less than capable diver. When divers in influential or leadership roles do this, it is a tremendous loss for the diving community in general—it robs future groups of divers of the opportunity to learn. Sadly, because this commonly happens at the leadership level, it is hardly surprising that other divers further down the line copy that behavior, and we ultimately end up with a diving culture that emulates the example of the leadership.
I advocate for taking the opposite approach. In my teaching, I am very open about the mistakes or errors I have made while diving. I recognize that I am basically a smart Roomba, and I learn by making mistakes. Thus, it would be disingenuous to pretend that I don’t make mistakes—I had to learn somewhere! I believe this approach lends authenticity to my instruction and starts to create psychological safety in my classes. Ultimately, my goal is to encourage students to recognize that, “If the instructor can admit they make mistakes, then it is okay to talk about the ones our team made during the training dive.”
I have found that there is a remarkable change in the relationship between student and instructor when this happens. Learning becomes more of a collegial activity, and stress and performance anxiety significantly decrease. This leads to more successful learning outcomes and happier students. I am a firm believer that, while training can be serious, it should also be fun!
Creating Psychological Safety
Creating psychological safety in our diving culture is a daunting task, but every flood begins with a single raindrop. The first thing that needs to happen—at all levels—is an acknowledgement of failures and mistakes among those in positions of influence and leadership. Sadly, this is not as easy as it sounds, and there is frequent pushback. Ego is one of the most dangerous aspects of a personality and it frequently causes people to overreach, crippling growth and learning. The irony here is that every single one of us has made a mistake. We all understand that no one is perfect, yet many in leadership positions cling to the view that vulnerability is weakness—that demonstrating imperfection will cause others to stop trusting them (or revering them).
I propose that the opposite is true. I should also note that I believe every dive professional is acting in a leadership role. This means that, while creating psychological safety can best be started by those in senior leadership roles, it must also be encouraged at all levels of leadership, including anyone in supervisory or teaching roles. In a perfect world, every diver would embrace this approach and enable psychological safety within their team.
There are a few things you can do to help develop psychological safety. First, facilitate a debrief at the end of the dive and begin with “something that I as the leader did wrong or could have done better was…” This immediately creates fertile soil for psychological safety to flourish. When the leader is the first person to say, “I made a mistake,” it establishes that this is a safe place to discuss mistakes and errors with the intention of learning from them. This opens the door to follow-up discussions.
On the subject of transparency, in any organization it is often the voice of dissent—a contrary position—that is the most valuable. This voice causes the group to reflect on original assumptions and decisions and offer a perspective that “groupthink” does not. This means that we need to be open to different solutions to problems lest we be blinded by our own cognitive biases—ones that have been developed over thousands of years of evolution in order to make us more efficient Roombas.
We are essentially fighting against our own brains, and it takes a significant amount of effort to think outside the box. We are hard-wired to think in terms of “evolutionary” rather than “revolutionary” ideas, and we need to make a conscious effort to consider the voice of dissent and understand why it is so hard to do so.

In Conclusion
In psychologically safe environments, we experience a significant increase in “discretionary effort,” or shifts on the “need to do” and the “want to do” curves. If a team has a high degree of psychological safety, they are motivated to perform higher than the minimum standard. If you create a high degree of psychological safety, your team will perform better as a result.
This is where it all comes full circle. We want our dive teams to perform at a high level. We want them to have a high degree of discretionary effort. We want them to embrace our “commitment to excellence.” Therefore, we must be the ones to create the psychological safety necessary to facilitate this growth.
One of the most effective things you can do as a leader is to be open and willing to share that, in the end, you are human too. You make mistakes, you admit to them, you learn from them, and you share them with others so they can learn too.
One of the most effective things you can do as a leader is to be open and willing to share that, in the end, you are human too. You make mistakes, you admit to them, you learn from them, and you share them with others so they can learn too.
DIVE DEEPER
Other stories by Guy Shockey:
InDEPTH: Reflections on Twenty Years of Excellence: Holding The Line (2019)
InDEPTH: Situational Awareness and Decision Making in Diving (2020)
InDEPTH: The Flexibility of Standard Operating Procedures (2021)
InDEPTH: How to Become an Explorer: Passion, Partnership, and Exploration (2022)
InDEPTH: Errors In Diving Can Be Useful For Learning— ‘Human Error’ Is Not! by Gareth Lock
InDEPTH: Learning from Others’ Mistakes: The Power of Context-Rich “Second” Stories by Gareth Lock

Guy Shockey is a GUE instructor and instructor trainer who is actively involved in mentoring the next generation of GUE divers. He started diving in 1982 in a cold mountain lake in Alberta, Canada. Since then, he has logged somewhere close to 8,000 dives in most of the world’s oceans. He is a passionate technical diver with a particular interest in deeper ocean wreck diving. He is a former military officer and professional hunter with both bachelor’s and master’s degrees in political science. He is also an entrepreneur with several successful startup companies to his credit.