Diving Deeper with Human Factors


More than 30 case studies combined with academic theory and detailed analysis to show how the events developed in the manner they did and what you can learn from them to improve your own diving.

"Understanding and integrating human factors into the practice of diving—the subject of "Under Pressure"—is the next frontier in improving diving safety and performance. As such, the book is a ‘Must-Read' for divers, team leaders and educators wanting to up their game.”

Michael Menduno/M2



Every one of us makes mistakes every day, even the experts.

For that very reason, the aviation, nuclear power and medical professions have invested huge resources in helping their personnel to get better at not making those mistakes, and if they do, how to capture them before it gets really bad. Now it's your chance to learn how they do it. This book demonstrates a new way of thinking and planning to avoid the errors that even the best of us make, errors that can cost lives.


"Accidents rarely “just happen”. As scuba divers, we are heavily dependent on our life support equipment to function properly, and we train and plan for our underwater excursions to anticipate certain failures. However, experience has shown that the “Human Factor” is the primary cause of most diving incidents. Everything is going well, until a seemingly innocent shift in procedure alters the course of the dive - through the cumulative consequences of bad habits, poor choices, and innate complacency - sometimes with tragic results.Utilizing case studies of actual diving incidents, alongside examinations compiled by other high-risk industries, “Under Pressure” seeks to remove the stigma surrounding the mistakes divers make, illuminate that errors are a critical part of our collective learning process, and that despite the level of one’s experience, not a single one of us is infallible. Regardless of your current experience as a diver, the use of non-technical skills and understanding of the Human Factors affecting both your choices and those made by others around you will positively impact your own underwater performance, and hopefully make your own diving safer."

Richie Kohler, Shipwreck Explorer, Author and Filmmaker.


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



If you buy the book from this site, you will be automatically added to the 'Under Pressure' community where you can discuss with other divers your successes, failures and opportunities for applying the knowledge in this book. Once you've paid for the book, you will be given access to the members area and can join in the discussions there.

"Reading ‘Under Pressure’ is a reassuring and humbling experience. Reassuring because it narrates many scenarios you could have been in but you were not because you used knowledge, common sense and gut-feelings to make a decision, a decision that often meant you had to stand tall facing peer pressure to do something different. Humbling because through the testimonials you learn that it doesn’t matter the number of dives you have or that you have a vast amount of experience, the combined decisions in a team and the operating conditions can always turn a great dive into a true challenge. 

‘Under Pressure’ is a must read for every diver and every instructor, to become more aware than you thought you could be so that your learning, processing and instinct come together to contribute to the best outcome when you’re faced with critical decisions which need to be made quickly and while under pressure. Even more important though, the knowledge contained within this book will help you avoid being in a situation where you need those skills!"

Ellen Cuylaerts, Award Winning Underwater Photographer and Conservationist.


“Under Pressure:Diving Deeper with Human Factors is a genuine game changer. There are many books about decompression theory, diving medicine and advanced diving techniques, but this is the only text that looks into the incredibly significant impact of Human Factors within diving. 

Gareth does a great job of taking the newest ideas in the fields of psychology, human behaviours and accident analysis and making them both entertaining and relevant to divers. The case studies from some well known diving personalities are fascinating and bring the book alive, illustrating some of the complex human factors concepts in a most accessible way.If you want to improve your diving, it is hard to think of a more cost effective way to do it than reading this book. If every diving course included a copy, recreational and technical diving would be a great deal safer and more enjoyable. If you are a diver, know a diver or want to be a diver: read it!"

Lanny Vogel, CCR, Cave and Technical Diving Instructor, Owner of Underworld Tulum.


Ordered copies will be sent as soon as I can. It might take a couple of days to pack up as I travel globally with work. If you need a copy more quickly than a few days, consider ordering from Amazon or Waterstones. To work out what this price is in your own currency, visit https://www.xe.com/



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If you want multiple copies, please get in touch directly with your address, the number and I will create a specific order for you. If you are an instructor or part of a training agency's staff and you'd like to include this book as pre-course reading for your classes, please get in touch. I am passionate about sharing my knowledge, we can talk about options to maximise learning and minimise cost.




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 https://www.thehumandiver.com



Steve Bogaerts, Ryan Booker, Heather Choat Armstrong, Tim Clements. Marc Crane. Garry Dallas. Andy Davis. Astrid de Jager. Matt Duke. Jill Heinerth. Gene Hobbs. Dr Dawn Kernagis PhD. Jon Kieren. Steve Lewis. Richard Lundgren. Michael Menduno. Jamie Obern. Clare Pooley. Reneé Power. Anton van Rosmalen. Cameron Russo. Joel Silverstein. Michael Thomas. Lanny Vogel. Dr Laura Walton CPsychol AfBPsS. Roger Williams. Plus a few more anonymous ones!