Scuba diving guides
How to choose each piece of gear, how the physics that governs a dive actually works, and where this site stops and formal training begins. Written for divers who want to understand the reasoning rather than be handed a conclusion.
The guides split into three kinds. Buying guides explain what separates a $350 regulator from a $750 one and when that difference matters. Physics and technique guides cover air consumption, buoyancy and weighting, which are the two areas where understanding the arithmetic changes the diving immediately. Ownership guides deal with maintenance and travel, which is most of what owning gear actually consists of after the purchase.
There is a fourth kind, represented by exactly one page: technical diving explained, which describes decompression diving, cave and wreck penetration and solo diving, says why each needs formal training, and then stops rather than publishing procedures.
- Air Consumption Guide: SAC Rate, RMV and DepthHow air consumption scales with depth: double at 33 feet, triple at 66, quadruple at 99. Work out your SAC rate, convert it to... Open →
- Buoyancy and Weighting Guide for Scuba DiversHow to weight yourself properly: do the weight check at the end of a dive with a near empty cylinder, float at eye level, and... Open →
- Dive Gear Buying Order: What to Buy FirstThe order to buy scuba gear in: mask first, then a dive computer, then exposure protection, then the regulator and BCD. What to... Open →
- Dive Travel Packing Guide: Weight, Carry-On, SparesDive travel packing: how to do the weight allowance arithmetic, why the computer and regulator ride in carry-on, what to rent... Open →
- How to Choose a BCD: Jacket, Back Inflate or WingHow to choose a scuba BCD: jacket versus back inflate versus backplate and wing, how much lift capacity you actually need... Open →
- How to Choose a Dive Computer: Buyer's GuideHow to choose a dive computer: what algorithms actually change, wrist versus console, when air integration is worth $400, and... Open →
- How to Choose a Scuba Regulator: Buyer's GuideHow to choose a scuba regulator: piston versus diaphragm, balanced versus unbalanced, sealed cold water first stages, DIN versus... Open →
- How to Choose a Wetsuit for Scuba DivingHow to choose a scuba wetsuit: thickness by water temperature, why fit beats millimetres, seam construction, hoods and gloves... Open →
- Nitrox Diving Guide: MOD, EAD and ppO2 LimitsNitrox explained: how to calculate maximum operating depth and equivalent air depth, why 1.4 ata is the working ppO2 limit and... Open →
- Scuba Diving for Beginners: Certification and GearWhat open water certification actually involves, what it costs, what you buy versus rent as a new diver, and the order to buy... Open →
- Scuba Gear Maintenance Guide: Rinse, Service, StorageScuba gear maintenance: the rinse protocol that actually works, annual regulator service, cylinder visual inspection yearly and... Open →
- Technical Diving Explained: What It Is and Where We StopWhat decompression, technical, cave, wreck penetration and solo diving are, why each requires formal training, and why this site... Open →
Which guide should you read first?
If you are newly certified, start with the gear buying order, because the most expensive mistake at that stage is buying the right things in the wrong sequence. If you are already diving regularly, start with the buoyancy and weighting guide: weighting is the single largest lever on air consumption, trim, ascent control and comfort, and most divers are carrying lead they do not need.
The numbers worth memorising
| Fact | Figure | Why it matters |
|---|---|---|
| Sea water per atmosphere | 33 ft | Every pressure calculation starts here. Fresh water is 34 ft |
| Gas use at 33 ft | 2x surface | At 66 ft it is 3x and at 99 ft it is 4x. The most useful fact a new diver can hold |
| Working oxygen limit | 1.4 ata | The bottom phase maximum. 1.6 ata is a contingency ceiling, not a target |
| Maximum ascent rate | 30 ft/min | Slower is better in the last 10 m |
| Safety stop | 3 min at 15 ft | On any dive to 30 ft or deeper |
| Recreational depth limit | 130 ft | Beyond it is technical diving, which needs its own training |
| Typical adult RMV | 0.4 to 0.75 cu ft/min | Roughly 11 to 21 litres per minute |
What order should you read these in?
There is a natural sequence, and it maps to the first two or three years of diving rather than to any curriculum.
- Before you own anything. Scuba diving for beginners and the gear buying order. The most expensive early mistake is buying the right items in the wrong sequence, usually a regulator before a computer, or a cylinder before either.
- While you are still renting most of it. Buoyancy and weighting and air consumption. These two are coupled: most high gas consumption is a weighting problem wearing a disguise, and fixing weighting is the single largest improvement available to most divers.
- As you start choosing gear. The four choosing guides, for the computer, regulator, BCD and wetsuit. Each explains what separates the price tiers and when the difference actually matters.
- Once you own it. Maintenance and travel, which together are most of what ownership consists of after the purchase.
- When you want more from a dive. Nitrox, which is the first specialty most divers take and the one that changes bottom time most, and then technical diving explained, which is where this site stops and a course starts.
What do these guides assume about you?
That you are certified, that you can handle a formula, and that you would rather see the working than be handed a conclusion. That is a deliberate choice about audience. Divers are a trained population, they will catch an error, and an error in this subject matter is dangerous rather than merely embarrassing, so the pages are written to be checked rather than trusted.
They also assume you are diving inside recreational limits: no planned decompression obligation, no overhead environment, a maximum of 130 feet. Where a topic crosses that line, the guides explain what it is and name the training rather than publishing a procedure. That limit is the subject of its own page and is stated in full on the safety disclaimer.