Depth Notes
Field notes and dive theory from the depths.
Decompression
How Decompression Models Work
May 28, 2025 · 14 min read
Your dive computer turns invisible dissolved gas into a single ascent number. Behind it sits a piece of bookkeeping: 16 imaginary compartments, the half-times that define them, and the M-values that decide when it's safe to come up.
Bubble Trouble
May 22, 2025 · 9 min read
Bubbles form on almost every dive. Two families of decompression model handle that differently, and the bubble models' headline idea, deep stops, failed the one test that counted: fewer measured bubbles did not mean less decompression sickness.
Gradient Factors
May 23, 2025 · 12 min read
The two numbers on your dive computer that decide how much supersaturation you carry to the surface: what they really are, why GF Hi is the one that actually sets your risk, and why a very low GF Lo is no longer considered safer.
GF99 and Surface GF Explained
June 16, 2026 · 6 min read
The two live numbers on your Shearwater most divers half-understand. GF99 is how supersaturated you are right now; Surface GF is what you'd hit if you surfaced this instant. What each means, how they move across a dive, and which one decides your ascent, with an interactive profile to scrub.
Safe Ascents
May 22, 2025 · 11 min read
Off-gassing needs a gradient, but too much of one foams. The soda-bottle rule of the ascent: the slowest, shallowest leg does the most work, because the proportional pressure change is biggest near the surface.
Decompression Procedures
June 15, 2025 · 15 min read
The actual job of a decompression diver: controlling the ascent, hitting planned stops, and switching to richer gas at the right depth. Where the math comes from, why the oxygen stop lives at 6 m, and which old rules of thumb survive scrutiny.
Dive Computers
Dive Computers: How They Actually Work
June 5, 2025 · 8 min read
What your dive computer is really doing under the display: how it remodels your nitrogen every few seconds, what each reading means, and the setup mistakes that turn a safety tool into a liability.
Living With Your Computer's Algorithm
June 12, 2025 · 7 min read
The practical side of the algorithm: why your computer nags you, how to live with an RGBM or bubble-model unit, and what to do when a mixed team's computers disagree.
Reading Your Dive Computer in Real Time
June 19, 2025 · 8 min read
How to use GF99 and Surface GF as live tools in the water, what the ascent-rate numbers really mean, and the things your algorithm simply cannot see.
Why Dive Computers Disagree
June 14, 2026 · 9 min read
Two divers do the exact same dive and surface with different no-stop times, different stops, and different no-fly clocks. That's not a fault — it's three decompression models talking. Here's why it happens, when it matters, and a live simulator that lets you watch it.
Rebreathers & CCR
Oxygen Toxicity
CNS Oxygen Toxicity
May 31, 2025 · 14 min read
Why the oxygen that keeps you alive can trigger a seizure underwater: what's really happening in your brain, the numbers that keep you safe, and why the famous warning signs don't actually warn you.
Pulmonary Oxygen Toxicity
June 1, 2025 · 7 min read
The slow, quiet form of oxygen toxicity: a sunburn for the inside of your lungs. What builds it up over long and repetitive dives, how OTUs track the dose, and why it's far more forgiving than the CNS kind.
Oxygen Toxicity & ROS
May 30, 2025 · 7 min read
The chemistry under every kind of oxygen toxicity: the reactive 'sparks' oxygen throws off, the cleanup crew that normally catches them, and why pressure, exercise, and CO₂ tip the balance toward damage.
Oxygen on a Multi-Day Trip
June 4, 2025 · 8 min read
Almost everything you're taught about oxygen toxicity is about a single dive. On an expedition or a liveaboard week the real question is cumulative, and it turns on a quirk: you run two oxygen clocks, and only one of them resets overnight.
Gas & Breathing
Inert Gas Narcosis
May 29, 2025 · 9 min read
What narcosis really does to your brain at depth, why the martini rule undersells the danger, and how nitrox and helium change the picture.
Gas Density and CO₂ Buildup
May 29, 2025 · 8 min read
Why breathing gas gets heavier with depth, how CO₂ creeps up even when you think you're breathing normally, and why it's one of the most underestimated risks in deep diving.
The Benefits of Nitrox
May 23, 2025 · 11 min read
Why enriched air is the highest-value course most divers never take: more bottom time, gentler repetitive days, less narcosis, and a free safety margin, set against the one real catch, oxygen.
DCS & Injury
Decompression Sickness (DCS): Causes, Symptoms, Prevention
June 16, 2026 · 10 min read
Decompression sickness, the bends, is what happens when dissolved gas comes out of solution as bubbles on ascent. What actually causes it, how to spot Type I vs Type II, what to do, and how to lower your risk.
Predisposing Factors for Decompression Sickness
June 3, 2025 · 12 min read
Why identical dive profiles produce different outcomes in different divers: the physiological, environmental, and behavioural factors that shift decompression risk beyond what any algorithm can predict.
What Actually Kills Divers
June 2, 2025 · 5 min read
Divers fear the bends, but it rarely kills them. The real causes of diving deaths are the heart and gas management. What the fatality data shows, and how to screen yourself for what actually matters.
Pulmonary Barotrauma & Lung Overexpansion Injury (AGE)
June 9, 2025 · 8 min read
Pulmonary barotrauma, the lung overexpansion injury, and how arterial gas embolism happens: why even a shallow ascent with a closed airway can cause a life-threatening emergency.
Flying After Diving: How Long Should You Wait?
June 16, 2026 · 4 min read
Fly too soon after diving and the nitrogen still in your body can bubble at altitude, even if you felt fine at sea level. Here are the actual wait times, why they exist, and why they're minimums, not targets.
Fitness to Dive
Fit to Dive
June 9, 2025 · 9 min read
How chronic conditions like asthma, diabetes, and heart disease interact with diving, why proper assessment matters more than any checklist, and what real-world dive fitness actually looks like.
Thermal Stress in Diving
June 8, 2025 · 8 min read
How being warm or cold changes nitrogen off-gassing during a dive, why the timing matters more than you'd think, why your dive computer can't see it, and what to actually do about it.
Immune Suppression and Diving
June 8, 2025 · 6 min read
Why long or repetitive diving can leave you run-down, what bubbles and oxidative stress have to do with your immune system, and how to recover properly between dive days. Honest about what's proven and what isn't.
Post-Dive Fatigue
June 9, 2025 · 6 min read
Why you're wiped out after diving: the physical work, the bubbles your body quietly cleans up, and the ordinary stuff like cold and dehydration. Plus how to recover, and how to tell normal tiredness from a warning sign.