Skip Navigation Website Accessibility

Under Pressure - Gareth Lock


Add to Cart

Most incidents and accidents are down to 'human error'. Unfortunately, 'human error' is normal and we can't get rid of it. However, we can reduce the likelihood of one of those, 'Oh s***t moments' if we have an understanding of human factors and develop our non-technical skills.

This is a globally-unique book containing decades of research and practice from high-risk domains translated into the world of recreational and technical diving. This is done through the use of numerous detailed case studies to highlight the value and applicability of these skills. This book is a must for all divers who want to manage their risks more effectively and have fun in the process. 

Gareth Lock, Author
Gareth Lock is a retired military aviator with a passion for improving safety and performance. Certified to advanced trimix level with GUE and to dive a JJ CCR through TDI, he has developed globally unique training programmes to bring the science of human factors to the diving domain to reduce accidents & incidents and improve the enjoyment of all divers. Last year he decided to condense the information he has learned and teaches and put it into this book. Although he is based in Malmesbury, UK, he travels the world speaking and training divers, healthcare professionals and oil & gas teams. If you'd like to know more about him, his work and his courses, visit


What you'll get from the book...

Detailed Case Studies

The book contains more than 30 detailed stories from globally-known divers such as Jill Heinerth, Richard Lundgren, Steve Bogaerts and Roger Williams. The case studies and analysis show how experts can make mistakes and through the application of experience (won the hard way) they survived to tell the tale.

Topics For All Divers

No matter if you are a beginner diver, an advanced wreck diver on CCR, a cave diver pushing the line on an exploration dive, or an instructor developing the future generations of divers, this book is for you. The details, skills and knowledge contained within this book are applicable to all divers, irrespective of your experience.

A Book with One Aim

To improve the safety and performance of divers. Too many divers don't understand how and why incidents happen. Often the incident is judged as 'human error'. If this happens, learning is limited and mistakes WILL happen again. Learn how humans really make decisions, how they should communicate and how we should all lead others.


Chapter 1: The Role of Human Factors and Non-Technical Skills in High-Performing Teams

Safety is boring! That’s why this book doesn’t focus on safety; it focusses on the skills and mindset required to be a high-performing diving team, individual diver or instructor/instructor-trainer. This chapter identifies what non-technical skills mean in the context of diving and why they are so important - using a number of examples of dives where things didn’t go to plan, but also how the application of the skills can create exciting and memorable dives, for the right reasons and not the wrong ones!

Chapter 2: Systems Thinking: The whole is greater than the sum of the parts

Systems thinking has been shown to be the most effective way of improving performance and safety. This is because while it is possible to improve specific components or people within a system, unless you look at their interactions with other people, equipment and the environment, you cannot make an improvement in the performance of the system.

In diving, there are numerous systems in place: a rebreather, diver, instructor, social and physical environment all make up a system. You can manufacture a rebreather which passes the required standards, but that doesn’t mean that it will be safe to use as a system (or part of a system), unless you take into account the components of the system.

This chapter will give you an overview of systems thinking and why it is essential to consider it if you want to improve your performance, your safety and the safety of others.

Chapter 3: ‘Human Error’ and why it isn’t that simple

Human error is a term often used as a 'catch-all', but has limited value when it comes to learning to improve. In the ’70s & ’80s, multiple research papers and presentations stated that 80% of aviation accidents were caused by 'human error'. Since the 1990s it has been recognised this attribution is flawed because 'human error' is normal and a ‘general’ term does not help learning from specifics.

This chapter will provide you with a summary of human error, error-producing conditions and why we need to search for the ‘rich-context’ stories if we want to improve.

Chapter 4: Risk Management or Gambling your life away

Much of diving is about risk management, but divers don't realise this because of the way in which the sport is portrayed; the suppression of diving incidents and accidents’ information; and the often adversarial and confrontational nature of near-miss discussions within the diving community when ’stupid’ mistakes are made.

This chapter will focus on risk; what it is; how we can manage it; and the biases we face when it comes to making ‘risk-based decisions’ in a dynamic environment. The aim isn't to scare divers, but rather to give them an indication as to how far we can drift and still think we are being safe.

Chapter 5: Just Culture and Psychological Safety

This chapter will highlight that without a Just Culture in place, learning is limited; and the same accidents/incidents will continue to occur with the individual divers often being blamed for the failure, rather than systemic factors. A Just Culture facilitates reporting and learning from adverse events leading to improved safety; whereas blame is the enemy of safety with incomplete stories being told, leading to poor incident analyses and sub-optimal behaviours when it comes to hiding near-misses.

Chapter 6: Decision-making

Decision-making has been defined as the process of reaching a judgement or choosing an option to meet the needs of a given situation. It can be broken down into the following main areas: understanding the situation at hand/defining the problem; determining a potential course of action or the option(s) available based on the information immediately at hand; selecting and executing that option; and then undertaking some form of review process to determine if the decision was effective in terms of the goals set.

This chapter will describe the different decision-making models and processes we use; their strengths and weaknesses; and how to overcome some of the cognitive limitations we have.

Chapter 7: Situational Awareness

Situational awareness is often talked about in diver training, but there isn't much detail about how it is developed and, more importantly, what can cause it to be 'lost'. Situational awareness is the concept by which we perceive data through our senses; process it so that we understand the here and now; and then using mental models of reality based on previous experiences, create a future model of what might happen. This is often simplified as What? So What? Now What?

This chapter will describe how the body/brain perceives information, the working memory and its associated strengths/weaknesses, before moving on to how your individual and team situational awareness can be improved in the context of diving.
Chapter 8: Communication

If only we could solve communication problems, then we wouldn't have any confusion or conflict! Communication sits in the middle of the model of non-technical skills and is crucial to high performance. Understanding the barriers and enablers to effective communication is essential if we are to improve performance and reduce error.

This chapter will focus on the different models of communication, how to decide which one to use and how to increase the likelihood of effective communication taking place through the use of different questioning techniques, briefs and debriefs.

Chapter 9: Teamwork and Teaming

A team is not a group of people who work together; rather, a team is a group who trust each other, and creating trust is a challenge in a peer-to-peer social environment and even harder without a clear leadership role being present. Teamwork is the core to high performance, because teams can achieve far more than just looking at the sum of its individual parts. However, teams don't just happen: they take time to develop and they all go through the same development process with conflict and frustration eventually leading to things 'just happening' when there is role clarity, effective communication and the need and want to hold each other accountable.

This chapter will focus on how to develop effective and high-performance dive teams using knowledge and understanding from the military, aviation and healthcare domains. It will also look at why teams fail and what can be done to address that. Fundamentally, effective teams understand the difference between teamwork and taskwork and develop their skills to meet both requirements.

Chapter 10: Leadership and Followership

Most groups have some form of leadership present, be that formal or informal. Leaders can easily set the tone, positively or negatively, within the group and effective followers will provide support. However, destructive goal pursuit, where the goal is more important than the safety and well-being of the team-members, combined with poor leadership, can easily lead to accidents or incidents. This is especially true with beginners who do not necessarily have the assertion skills and don't recognise the authority gradient which is present.

This chapter will focus on leadership and leadership styles in the context of diving and how knowledge of these can improve diving enjoyment, goal attainment and instructional abilities. The chapter will also cover the topic of followership and why it is so important in a recreational activity where decisions need to be made considering a team and not just individuals.

Chapter 11: Performance Shaping Factors

You can have the best technical skills in the world and be able to apply a high level of technical and non-technical skills, but if you don't understand the impact of stress and fatigue on your own and others' performance, then you are destined to failure.

This chapter will provide divers, especially supervisors, an overview of how stress and fatigue shape human performance and what can be done to manage these factors thereby improving diving safety. Furthermore, linking with the chapter on human error (chapter three), error-producing conditions will be covered in more detail here.

Chapter 12: Living with Failure

Failure is everywhere. However, we cannot innovate or improve if we don’t fail. Despite this, failure has been given an incredibly negative attribution by most parts of modern society, normally because something has been lost or didn’t reach fruition, be that a goal, money or a tangible product. What if we turned it around so that learning from failure was seen as the key to improvement? What if we looked at the failed processes and unsuccessful outcomes as lessons and opportunities to learn and not just identify where the failures happened?

This chapter will focus on learning from experience and will give you specific tools whereby you can apply 20:20 hindsight before a major trip or expedition, or use learning reviews to understand what really happened - rather than what should have happened. Telling stories about things which didn’t happen doesn’t help learning.

Chapter 13: Bringing it all together

This chapter will summarise the learning points from each of the chapters and provide readers with quick wins on how to apply the contents of this book into their own diving, instruction and leadership.

  • 690 Radford Street
    Christiansburg, Virginia 24073
  • Text/Call: (540) 315-1020
  • Email:
  • Hours: Mon - Thu  |  11:30 - 5:30
                 or by appointment