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.



Każdy z nas popełnia błędy każdego dnia,
nawet eksperci.


Z tego właśnie powodu lotnictwo, energetyka jądrowa i służba zdrowia zainwestowały ogromne środki, aby pomóc swojemu personelowi w
nie popełnianiu tych błędów.

A jeśli już zostaną one popełnione, to jak je wykryć, zanim zagrożą
bezpieczeństwu jednostek i organizacji i staną się przyczyną katastrof.
Teraz macie szansę dowiedzieć się, jak to się robi. Ta książka demonstruje nowy sposób myślenia i planowania, aby uniknąć błędów, które popełniają nawet najlepsi z nas, błędów, które mogą kosztować życie.



"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.

"Under Pressure is a life book. Exactly. To me, it ranks with “Deep Survival” by Laurence Gonzales as the most influential book on my way of doing things. I read Deep Survival when it was first published. Changed everything. And so has Under Pressure. Upped the game. Especially on method.

Deep Survival is much about comprehension, but no method. You can derive methods from it, and effectiveness of method anyway starts with the deep understanding of the need for it. I added GUE method to all my activities. Now broadened with Just Culture etc. So grateful to you. Saving many lives, and improving even more of them. A lot.

When you operate inside these frameworks you can have clear and present awareness of your surroundings in such a relaxed way. Much more delight. Which is why we dive and live, after all."

Susanne Williams. Explorer. Diver.


“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.


As lockdown is easing, you can now order copies from me directly and I will send them out signed.

You can also get Audible and Kindle/iBooks versions by searching the relevant online stores.



Pick-up or In-Person Only 




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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!