Diving guides that do the math

Pressure and ATA Basics for Scuba Divers

Build the pressure foundation behind gas use, partial pressure, buoyancy, and decompression with worked metric and imperial examples.

Understanding SAC Rate: Why It Matters for Every Diver

Learn what Surface Air Consumption rate is, how to calculate it, and tips to improve your breathing efficiency underwater.

Scuba Cylinders Explained: Sizes, Materials, and Buoyancy

What cylinder labels really mean, how working pressure sets the gas you carry, and why aluminum, steel, and composite cylinders behave differently in the water.

Scuba Diving Units: Bar, PSI, Meters, and Feet

Convert the units divers use, understand which conversions are exact or approximate, and avoid mixing pressure, depth, and cylinder capacity.

Turn Pressure and the Rule of Thirds

Calculate a usable turn pressure, distinguish thirds from minimum gas, and choose the earlier limit for direct-ascent and return-to-exit dives.

Rock Bottom Gas: How Much Reserve Do You Really Need?

Calculate minimum gas for a two-diver emergency ascent and learn how depth, breathing rate, and cylinder size change reserve pressure.

Nitrox Blending: Oxygen, Air, and Residual Gas

Learn how partial-pressure and continuous Nitrox blending account for residual gas, and why every calculated fill must still be analyzed.

How Long Will My Scuba Tank Last?

Estimate cylinder duration from usable gas, depth, and RMV, and understand why a constant-depth estimate is not a complete dive plan.

Diving Gases Explained: Air, Nitrox, Trimix, Heliox, Oxygen, and Argon

Understand the breathing and inflation gases divers encounter, what each one does, and why depth and exposure determine whether a mix is suitable.

SAC Rate vs RMV: What's the Difference and When to Use Each

Understand the difference between SAC rate and RMV, when to use each metric, and how to convert between them.

Equivalent Air Depth (EAD) Explained

Work out the air depth a Nitrox dive is decompression-equivalent to, and see why EAD never changes your oxygen limit.

CNS Percentage and OTU: Tracking Oxygen Exposure

Learn how the CNS clock and OTU loading track oxygen exposure across a dive and a diving day, and what the limits mean.

Best Nitrox Mix for Any Depth

Calculate the richest theoretical Nitrox mix for a planned depth and PPO2 limit, then learn how to apply the result safely.

Nitrox Blending: Oxygen, Air, and Residual Gas

Learn how partial-pressure and continuous Nitrox blending account for residual gas, and why every calculated fill must still be analyzed.

Understanding MOD: Maximum Operating Depth Explained

Learn what Maximum Operating Depth means, how MOD is calculated from oxygen percentage and PPO2 limits, and how to apply it in real dive planning.

Diving Gases Explained: Air, Nitrox, Trimix, Heliox, Oxygen, and Argon

Understand the breathing and inflation gases divers encounter, what each one does, and why depth and exposure determine whether a mix is suitable.

What is Nitrox? A Complete Guide for Divers

Learn what Nitrox is, how enriched air works, its benefits and risks, and why divers choose it.

Diving Safety: Essential PPO2 Limits Every Diver Should Know

Understand partial pressure of oxygen limits, oxygen toxicity risks, and how to stay safe at depth.

Equivalent Air Depth (EAD) Explained

Work out the air depth a Nitrox dive is decompression-equivalent to, and see why EAD never changes your oxygen limit.

Surface Intervals and Repetitive Dives

Understand residual nitrogen between dives, how surface intervals restore no-stop time, and the rules for flying after diving.

No-Decompression Limits and Safety Stops

Learn what an NDL represents, compare modelled air and Nitrox limits, and understand how ascent rate and safety stops fit into the plan.

Pressure and ATA Basics for Scuba Divers

Build the pressure foundation behind gas use, partial pressure, buoyancy, and decompression with worked metric and imperial examples.

Scuba Cylinders Explained: Sizes, Materials, and Buoyancy

What cylinder labels really mean, how working pressure sets the gas you carry, and why aluminum, steel, and composite cylinders behave differently in the water.

Scuba Diving Units: Bar, PSI, Meters, and Feet

Convert the units divers use, understand which conversions are exact or approximate, and avoid mixing pressure, depth, and cylinder capacity.

Scuba Buddy Checks and Predive Safety

Turn the familiar buddy check into a practical team briefing covering gas, releases, weights, computers, route, limits, and emergencies.

Nitrogen Narcosis: Signs and Management

Understand what causes narcosis, calculate trimix END under an explicit convention, and learn the habits that keep impairment manageable.

Weighting and Buoyancy Control

Find a weighting that lets you hold a stop at the end of a dive, and understand why cylinders and suits change the answer.