The first time someone told me a scary underwater story, it didn’t end with gadget failure or textbook error—it ended with a shrug and, “we were just…distracted.” That stuck with me. Years later, stumbling across Gareth Lock’s “Under Pressure,” I realized that the real stories in diving—those close calls, near-misses, or “how did that go wrong?” moments—are less about equipment, and more about what’s swirling inside our heads. This book isn’t your average dive manual. It’s a brave look at how human factors, decision quirks, and good old-fashioned team dynamics shape every single dive, for better or for much, much worse.

Stop Blaming ‘Human Error’: The Evolution of Dive Incident Analysis

For decades, the phrase “human error” has dominated Dive Incident Analysis. When something went wrong underwater, the explanation was often quick and simple: a diver made a mistake. But as Gareth Lock’s Under Pressure: Diving Deeper with Human Factors reveals, this mindset is outdated and dangerously incomplete. The book draws on over 30 real-world Diving Accident Case Studies to show that context—habits, team dynamics, and system quirks—matters far more than most divers realize.

Lock traces the history of incident investigation, highlighting how, since the 1970s and 1980s, “human error” became a convenient catch-all. This approach, he argues, misses the deeper story. In the 1990s, both aviation and healthcare began to shift their focus, recognizing that labeling incidents as “human error” actually prevents genuine understanding and improvement. Diving is finally catching up, thanks in large part to Lock’s work.

Beyond Blame: The Power of Root Cause Investigation

Instead of blaming a single diver, Lock urges the community to look for the chain of events, assumptions, and system weaknesses that lead to incidents. He writes,

“Accidents are rarely acts of God—they’re products of overlooked cues and cultural blind spots.”

This perspective is echoed by industry leaders and is a recurring theme throughout the book.

Take, for example, a night dive incident featured in one of Lock’s case studies. A diver fumbled a mask switch, an error that was initially chalked up to personal negligence. However, Root Cause Investigation revealed a different story: poor team coordination, unclear communication, and a lack of pre-dive checks all contributed to the mishap. The “error” was not just a slip of the hand, but a symptom of a much larger system breakdown.

Systems Thinking: Context Is Everything

Lock’s analysis draws direct parallels to high-risk industries like aviation, where Dive Incident Analysis has evolved to include Human Factors and Systems Thinking. He shows that effective safety isn’t just about technical skills or equipment, but about understanding how divers, instructors, and even the environment interact as an interconnected system. When incidents occur, it’s rarely due to a single bad decision—instead, it’s a web of small, often invisible, factors.

• Human Factors: How team dynamics, communication, and decision-making shape outcomes

• Systems Thinking: Viewing incidents as the result of multiple, interacting elements

• Root Cause Investigation: Digging deeper than “human error” to find the real reasons behind mistakes

By dissecting the “local rationality” behind each diver’s actions, Lock demonstrates that what looks like a bad decision in hindsight often made sense in the moment, given the information and pressures at play. This nuanced approach, supported by detailed Diving Accident Case Studies, is what sets Under Pressure apart as a game changer for Dive Incident Analysis.

The Underwater Team Mind: Building Safety through Non-Technical Skills

Gareth Lock’s Under Pressure: Diving Deeper with Human Factors brings a fresh perspective to dive safety by spotlighting the often-overlooked power of non-technical skills for divers. While traditional training focuses on gear, gas, and procedures, Lock’s work—endorsed by industry leaders like Mark Powell, Phil Short, and Jill Heinerth—shows that teamwork, communication, and trust can make or break a dive, especially when no one’s officially “in charge.”

Diving Team Safety: More Than Just Equipment

Lock’s analysis of real-world incidents reveals a simple truth: technical skills alone are not enough. Many accidents stem from subtle lapses in communication or teamwork, not just equipment failure. As Steve Lewis puts it,

“Human factors aren’t just fluff—they’re often the reason dives succeed or fail.”

Drawing on lessons from aviation and healthcare, Lock demonstrates that even the best-trained individuals can make mistakes without strong team support. In diving, where teams are often peer-based and leaderless, this means every diver must be ready to speak up, share concerns, and listen actively.

Communication Strategies for Dive Teams

• Clear Hand Signals: Don’t assume your buddy knows what you mean—agree on signals before the dive.

• Pre-Dive Briefings: A simple, honest discussion about the plan, roles, and “what-ifs” sets the stage for safer dives.

• Debrief Openly: After the dive, talk about what went well and what could be improved. This is where real learning happens.

Lock’s practical tip: “Clear hand signals and briefings beat silent assumptions every time.” These communication strategies for dive teams help prevent confusion and reduce the risk of error.

Just Culture in Diving: Building Trust and Psychological Safety

A standout theme in Under Pressure is the call for a Just Culture in diving. Instead of blaming individuals for mistakes, Lock advocates for an environment where divers feel safe to report near-misses and errors. This approach, borrowed from high-risk industries, encourages honest discussion and learning, not punishment or shame.

By promoting psychological safety, teams can address the root causes of incidents—whether it’s a missed signal, a moment of complacency, or a misunderstood plan. Lock’s vision is clear: “All mistakes deserve a safe space for discussion, not a witch-hunt.”

Non-Technical Skills for Divers: The Real Game Changer

Lock’s research shows that situational awareness, leadership, and followership are just as vital as knowing your dive tables. By integrating these non-technical skills for divers into training and daily practice, teams become more resilient and adaptable—qualities that save lives when things go sideways underwater.

Under Pressure makes a compelling case: to truly improve diving team safety, divers must look beyond bubbles and embrace the human side of the sport.

Beyond the Checklist: Systems Thinking and the Invisible Factors That Shape Decisions

“Under Pressure: Diving Deeper with Human Factors” by Gareth Lock brings a fresh, much-needed perspective to Systems Thinking in Diving. The book challenges the old-school idea that safety is just about ticking off checklists or relying on high-end gear. Instead, Lock shows that true dive safety comes from understanding how equipment, training, environment, and human habits all interact—because, as the book makes clear, no diver is an island.

Lock’s approach goes far beyond the standard “Did you check your O-rings?” mentality. He urges divers and instructors to look at the bigger picture: How do policies, gear design, fatigue, stress, or even peer pressure combine to shape decisions underwater? This is the heart of Risk Management in Diving—recognizing that incidents rarely have a single cause. Instead, they emerge from a web of interconnected factors, many of which are invisible or overlooked in traditional training.

A standout feature of the book is its use of models inspired by GUE Methods Diving Safety and root cause analysis frameworks. Lock makes complex psychological concepts practical and accessible, even for weekend divers. For example, he explains how a top-of-the-line rebreather (like those certified by JJ CCR or GUE standards) is only as safe as the diver’s mental state. A tired, distracted diver can turn even the best equipment into a liability. As Jill Heinerth puts it:

“Fixing one broken part rarely makes a team safe; understanding the whole system does.”

This systems thinking lens encourages divers to see every dive as a dynamic interaction between people, technology, and the environment. Lock’s case studies—drawn from real-world incidents and featuring respected names like Jill Heinerth and Steve Bogaerts—reveal how small lapses, ingrained habits, or cultural pressures can quietly undermine safety. The book’s analysis shows that technical fixes alone are not enough; Human Factors Skills like communication, situational awareness, and stress management are just as critical.

Lock also highlights the importance of “Just Culture”—a framework that supports open reporting and honest discussion of mistakes without blame. This approach, borrowed from aviation and healthcare, helps teams learn from near-misses and failures, rather than sweeping them under the rug. By fostering psychological safety, divers are more likely to speak up about risks, share lessons, and improve together.

With clear explanations, practical tools, and actionable insights, “Under Pressure” makes systems thinking a core part of modern dive safety. The book’s integration of GUE and JJ CCR standards, along with its focus on both technical and human limitations, sets a new benchmark for risk management in diving. For divers and instructors seeking to move beyond checklists and truly understand what shapes decisions underwater, Lock’s work is an essential, game-changing read.

When Things Go Wrong: Learning from Failure, Not Hiding It

In the world of diving, mistakes are inevitable—but what matters most is how the community responds when things go wrong. Under Pressure: Diving Deeper with Human Factors by Gareth Lock boldly reframes failure, arguing that hiding mistakes can be far more dangerous than making them. Instead of sweeping errors under the rug, Lock’s approach encourages divers to see every mishap as a vital learning opportunity, not a source of shame.

Lock’s case studies are refreshingly honest, sometimes even cringe-worthy in their detail. Each story is a real-world example of how small lapses—like a missed checklist item or a misunderstood signal—can spiral into serious incidents. But rather than assigning blame, Lock uses these stories to highlight the value of Learning from Failure. He demonstrates that when divers openly share their experiences, the entire community benefits from the lessons learned.

“Our greatest instructor is often our toughest mistake.” — Gareth Lock

One standout story involves a diver’s near-miss in poor visibility. Instead of keeping quiet, the diver led an open debrief with the team. By breaking down what went wrong—miscommunication, assumptions, and a moment of panic—the group identified practical changes for future dives. This honest review didn’t just prevent future errors; it built trust and improved the team’s Human Factors Skills like situational awareness and communication.

Lock’s emphasis on a Just Culture Approach is clear throughout the book. Rather than punishing individuals for honest mistakes, a Just Culture promotes psychological safety. Divers feel empowered to report near-misses and errors, knowing they’ll be met with support and curiosity, not judgment. This shift is crucial: research from aviation and healthcare shows that open discussion of errors is key for practical safety improvement. By normalizing transparent storytelling, Lock helps break down the cultural barriers that have long discouraged divers from admitting mistakes.

Storytelling and community support are critical elements for changing diving culture. That’s why Lock champions the Under Pressure online community. This unique platform extends the book’s philosophy beyond its pages, offering a safe space where divers can share their wins, losses, and hard-won lessons. It’s a living example of Diving Community Support in action—a safety net where no one has to face failure alone.

• Failure isn’t a dirty word: In diving, hiding mistakes could be worse than making them.

• Case studies become group lessons: Honest, sometimes uncomfortable stories help everyone grow.

• Open debriefs drive change: Teams that talk about near-misses build lasting improvements.

• Community support matters: The Under Pressure network keeps the conversation—and learning—alive.

Lock’s approach turns errors into teaching tools, promoting a shift toward learning, openness, and mutual aid in the diving world. By embracing failure as a catalyst for growth, Under Pressure sets a new standard for safety and support in diving.

Wearing Many Hats: Gareth Lock’s Crossover Lessons for Diving (and Beyond)

Gareth Lock’s Under Pressure: Diving Deeper with Human Factors stands apart not just for its content, but for the unique authority Lock brings to the table. As a retired military aviator, GUE and TDI JJ CCR-certified diver, and global educator, Lock’s career has taken him from the cockpit to the ocean depths and into high-stakes industries like healthcare and oil & gas. This diverse background is the foundation for a book that speaks with equal credibility to pilots, doctors, oil platform teams, and underwater explorers. The result is a set of diving training materials and leadership principles that are as practical as they are profound.

Lock’s approach is all about reframing how we see mistakes. Instead of blaming individuals for “human error,” he urges readers to consider the context—what led to the decision, what pressures were at play, and how the system shaped the outcome. This perspective, borrowed from aviation and other high-risk professions, is a game changer for diving leadership. As Mark Powell puts it,

“Safety is a journey, not a box to check.”

Lock’s book and workshops make this journey accessible, offering tools that help teams in any field learn from failure rather than hide it.

The influence of the Gareth Lock Book stretches far beyond the pages. His training materials, available through The Human Diver and Amazon, have been adapted for use by healthcare professionals and oil & gas workers—proving that the lessons of diving safety are universal. One dive instructor in Brazil shared that the book made him rethink how he teaches students to respond to stress, showing just how far Lock’s reach extends. The practical edge of his work comes from real-world case studies, candid storytelling, and a focus on actionable change, not just theory.

Lock’s workshops and resources encourage a culture where divers, doctors, and engineers alike can talk openly about near-misses and mistakes. This shift—from blame to learning—creates safer teams and better outcomes, whether underwater or in the operating room. The book’s clear structure and accessible language make it a must-read for divers at every level, and its cross-industry insights ensure that even seasoned professionals will find something new to consider.

With Under Pressure available as a signed physical copy, on Kindle, Audible, and iBooks, there’s no excuse not to pick it up. Lock’s blend of adventure, research, and practical wisdom sets a new standard for diving training materials and leadership principles. In the end, his message is simple but powerful: safety isn’t about ticking boxes—it’s about understanding people, systems, and the stories behind every decision. That’s a lesson worth carrying, both in diving and beyond.

TL;DR: In a nutshell: “Under Pressure” flips the script on diving safety by spotlighting the human side of risk, turning errors into opportunities for learning and pushing us all to dive a little smarter—together.