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Scuba diving, explained simply.
Straight, accurate answers to the questions new divers actually ask — written to help you understand, not just memorise. When you’re ready to pass your exam, the OpenWater Pass System pulls it all together.
📖 Scuba diving glossary — every exam term defined →Skills & Safety
Equalize your ears by gently adding air to your middle ears as you descend — pinch your nose and softly blow, early and often, before you feel any pain.
Why can't you hold your breath when scuba diving?Never hold your breath on scuba because the air in your lungs expands as you ascend — trapping it can over-expand and injure your lungs. Breathe continuously at all times.
How does buoyancy work in scuba diving?Buoyancy in scuba is controlled with a BCD (buoyancy control device) and your breathing: add air to float, release air to sink, and fine-tune with your lungs to hover weightlessly — called neutral buoyancy.
Dive Planning
A no-decompression limit (NDL) is the maximum time you can stay at a given depth and still ascend directly to the surface (with a safety stop) without required decompression stops.
Dive tables vs dive computer — what's the difference?Dive tables are printed charts you use to plan no-decompression limits by hand before a dive; a dive computer tracks your actual depth and time live and recalculates your limits continuously.
Certification
An entry-level Open Water certification typically qualifies you to dive to 18 metres (60 feet). With further training you can extend your limit toward the recreational maximum of 40 m (130 ft).
What to expect in your Open Water courseAn Open Water course has three parts: knowledge development (theory and a written exam), confined-water training (pool skills) and open-water dives. It usually takes 3–4 days and certifies you to 18 m (60 ft).
PADI vs SSI vs NAUI — which should you choose?PADI, SSI and NAUI all produce internationally recognised, cross-honoured certifications with the same depth limits and core theory. The biggest difference is the dive centre and instructor, not the agency.
Scuba certification levels, explainedRecreational scuba builds in stages: Open Water (18 m), Advanced Open Water (30 m), Rescue Diver, then pro levels like Divemaster — plus specialties such as Nitrox and Deep.
What is nitrox diving?Nitrox (enriched air) is breathing gas with more oxygen and less nitrogen than air. It extends your no-decompression limits, but has its own shallower depth ceiling because of oxygen — and needs a short specialty course.