Scuba Diving — Glossary

Every Scuba Diving term explained in plain language: technique, equipment, rules and slang – with tips on avoiding the classic mistakes.

Buoyancy Control (Movement): The state of hovering in the water without sinking or rising. You set it coarsely with the BCD and fine-tune it purely through lung volume.
Frenzel Manoeuvre (Movement): Equalising with the base of your tongue instead of your lungs: you drive the small pocket of air in your mouth towards the middle ear. Reliable to 25–30 metres, and beyond with training.
Nitrogen Narcosis (Slang): The boat-deck word for the narcotic effect of nitrogen under pressure. It usually sets in from 25 to 30 metres and feels like two or three beers too many.
No-Decompression Limit (Rule): How long you can stay at a given depth before mandatory decompression stops become unavoidable. Your dive computer recalculates it continuously.
Safety Stop (Rule): The standard pause at the end of a dive: around 5 metres, typically 3 to 5 minutes — even when you never came close to your no-deco limit.
Silt-out (Slang): When fine sediment lifts and visibility drops to zero within seconds. Usually it is not the cave that causes it but your own fin kick.
Stop – Breathe – Think – Act (Cheat code): The four steps that break the panic chain: stop, breathe slowly and deliberately, assess, and only then act. In that order, without exception.
Trim (Movement): How your body is angled in the water — the goal is horizontal, with shoulders, hips and knees in one line. Buoyancy controls your depth, trim controls your attitude.

General

Terms from training theory that apply in every sport.

1RM (One-Repetition Maximum) (Rule): The maximum weight you can move for exactly one clean repetition. The reference value behind almost every training plan.
BMR & TDEE (Rule): BMR is your basal metabolic rate at complete rest; TDEE is total daily expenditure including everyday movement and training. Nutrition targets always work off TDEE.
Cadence (Movement): Steps per minute when running, or pedal revolutions when cycling. For most runners, 170–180 steps per minute sits in the sweet spot.
Core Tension (Movement): Active stabilisation of abdomen, back and pelvis — the bridge that lets force travel between legs and arms at all.
Deload (Cheat code): A deliberately lighter week with volume or intensity clearly reduced, so adaptation can catch up.
DOMS (Delayed Onset Muscle Soreness) (Cheat code): Delayed muscle soreness 12–72 hours after unfamiliar load. Not a measure of training quality.
Knee Valgus (Movement): The knees collapsing inward during squats, jumps and landings. One of the key risk markers in technique analysis.
Progressive Overload (Cheat code): The one principle no training works without long-term: the stimulus has to grow over time, otherwise adaptation stops.
RIR (Reps in Reserve) (Rule): How many clean reps you had left at the end of a set. RIR 2 means two more were available.
RPE (Rate of Perceived Exertion) (Rule): A scale for perceived effort. In strength training it usually runs 1–10, where RPE 8 means you had two more reps in the tank.
Zone 2 (Aerobic Base) (Cheat code): The easy endurance zone where you can still hold a conversation in full sentences. The base of almost every endurance plan.