Decision Making & Situational Awareness — The Human Side of Safe Diving (part 2)
Our June safety topic, Beyond Buoyancy Control: The Human Side of Safe Diving, centered on a publication shared by Les: Top Tips for Beginner Divers, written by Gareth Lock, Mike Mason, and Pedro Paulo “PP” Cunha of The Human Diver. If you missed the download instructions, you’ll find them in the June 2026 blog on the Michigan SeaSnoopers site.
At the June meeting, members were asked to read the publication and bring back at least one key takeaway or personal dive experience related to the topics covered. This month, I’m focusing on two sections that stood out to me: Decision Making and Situational Awareness. There are many more valuable insights in the publication, so feel free to bring any related discussion points to the July or August meetings.
What Are “Human Factors,” Anyway?
As a quick refresher from last month: human factors is the study of how real humans — with real limitations, habits, and quirks — interact with systems, tools, and environments. These principles are used in aviation, healthcare, manufacturing, software design… and yes, diving.
The Human Diver, founded by Gareth Lock, applies these ideas to our world underwater. Their core message is simple:
Most diving incidents stem from human error, not equipment failure. Improving communication, decision‑making, situational awareness, and teamwork reduces risk.
Decision Making: Why Smart Divers Sometimes Make Bad Choices
Author’s note — I’ll emphasize this applies to divers of all experience levels:
Two Biases That Trip Us Up
The publication highlights two cognitive biases that often influence divers:
- Sunk Cost Bias When we’ve invested time, money, or effort, we feel pressure to “make it worth it” — even if continuing is unsafe.
- Plan Continuation Bias Under stress or social pressure, humans tend to stick to the original plan even when conditions change or warning signs appear
Scenario: The $500+ Weekend Problem
You finally make it onto a Lake Huron charter after a hectic month. The weekend will cost you $500 or more. On the first dive, your Shearwater transmitter dies. Your computer still works, but you have no idea how much gas you have. Now what?
Questions you might ask yourself:
- Should I thumb the dive? I’ll waste all this money and disappoint my buddy.
- How will I explain to my partner that I spent all this time and money and had to abort?
- Will the captain or other divers think I don’t belong here?
Rationalizations you might make:
- I breathe slowly — I’m sure I have enough gas for 35 minutes.
- I won’t tell my buddy; she’ll freak out.
- Toughen up buddy, uncertainty is part of diving.
This is exactly where human factors matter. Recognizing these thoughts — and choosing safety over sunk costs — is what separates a good dive from a dangerous one.
Meeting Discussion and Self‑Reflection: Decision Making
Think about how you make choices underwater — and what influences them. Use these prompts to explore your own decision‑making habits before our next club discussion.
- Think about a dive where you pushed forward even though something felt “off.” What stopped you from calling the dive or changing the plan?
- What kind of diver are you right now — the one who pauses to reassess, or the one who keeps going and hopes it’ll work out?
- Have you ever assumed someone else (buddy, guide, instructor) had everything under control — and later realized they didn’t? What did you learn from that?
- What’s one decision point you can clearly define before your next dive? (Example: “I will let my buddy know when I use 1/3 tank,” or “I will pay attention to my buddy to not lose sight.”)
Situational Awareness: A Skill Worth Building
Situational awareness is the ability to notice what’s happening, understand what it means, and anticipate what might happen next. The authors break it into three parts:
- Perception — “I’m swimming hard but not making progress.”
- Comprehension — “There’s a current.”
- Projection — “I’ll use more gas than usual.”
Awareness is only useful if you act on it. In the current example, that might mean communicating with your team, adjusting depth, using the environment for shelter from the current, or changing the dive plan.
A Personal Example: The Chisholm Engine Dive
One of the dives off of Isle Royale is the Chisholm’s double‑expansion steam engine in Lake Superior. I dove with 27% nitrox to a max depth of 139 feet with a bottom temperature of 40°F. At maximum depth, my NDL was down to 2 minutes. As we ascended gradually along the engine from 127′ to 55′, I continued to on‑gas and hit an NDL of 0 minutes.
The dive was planned as a no‑decompression dive, and I stuck to the plan. But doing so required intense focus on depth, ascent rate, and NDL. Not having a lot of experience at these depths, I felt that this was the best use of my attention. The trade‑off? I don’t have a strong visual memory of the dive site — my attention was on the numbers.
Reference: Chisholm Engine
A Wreck That Tests Your Awareness: The North Star
The North Star in Lake Huron is a great wreck for practicing situational awareness. It’s disorienting, broken apart, and often murky with 20–25′ visibility. I’ve dove it several times, and on one dive my buddy and I couldn’t find the up‑line — we ended up deploying a dSMB.
On my most recent dive, I made a point of mentally mapping the wreck:
- The down line is attached to part of the triple‑expansion engine (A).
- Two large boilers sit off the starboard side (B).
- Follow the solid red line towards the bow. The bow has detached and may not be visible from the main wreck.
- Returning along the port side and following the debris field (dashed red line) can result in one missing the boilers or engine entirely.
Reference: Shipwreck North Star | 3DShipwrecks.org
Tools to Stay Oriented
- Set one or more strobes on the down line or near key “landmarks”.
- Run a line in limited visibility.
- Look back periodically to see where you came from. That is where you will be headed on the return trip.
Questions to Ask Yourself
- Have you ever said, “You lead, I’ll just follow”? What could go wrong?
- How often do you practice skills while task‑loaded? (Deploying a dSMB with neutral buoyance is perfect for this.)
- Have you ever checked your SPG or computer and been surprised? Before checking, predict what you expect — then confirm.
Meeting Discussion and Self‑Reflection: Situational Awareness
Situational awareness is a skill — and every dive gives you a chance to sharpen it. These questions can help you identify where your awareness is strong and where it can improve.
- During your last dive, was there a moment when you realized you had no idea about your depth, gas, or direction? What caused that lapse in awareness?
- What small habit could you start doing right now to improve your situational awareness? (Examples: gas checks every X minutes, scanning for your buddy more often, predicting your SPG reading before checking.)
Summary
This month’s safety blog builds on The Human Diver’s insights into how human factors influence diving safety. It highlights two critical areas: decision making — where stress, task loading, and cognitive biases can push divers toward unsafe choices — and situational awareness — the skill of perceiving, understanding, and anticipating underwater conditions. This blog encourages everyone to read the full article, to reflect on their own habits and share experiences with the club or leave a comment.
