What Is Scuba Diving? Types of Diving Explained for Beginners

Scuba diving means swimming underwater while breathing from a tank of compressed air that you carry on your back. The word is an acronym: Self-Contained Underwater Breathing Apparatus. "Self-contained" is the important part. Unlike older helmet divers, who were connected to the surface by a hose, a scuba diver carries their own air supply and moves freely.

For most people, scuba diving is a holiday activity and a lifelong hobby. You don't need to be an athlete, and you don't have to go deep. Most of the colour and life on a coral reef sits in the top 5 to 18 metres, where light is strongest. That is exactly the depth range beginner courses teach you to dive in.

How scuba diving works in plain English

A scuba set has four main parts that work together:

• The tank (cylinder) holds air compressed to around 200 bar. That is roughly 200 times normal atmospheric pressure, enough for a relaxed 45 to 60 minute dive at shallow depth.
• The regulator reduces that high pressure in two stages and delivers air to your mouthpiece only when you breathe in, at exactly the pressure of the water around you. That is why breathing underwater feels surprisingly normal.
• The BCD (buoyancy control device) is a jacket you can inflate or deflate with the push of a button, so you can float at the surface and hover weightlessly underwater.
• Weights offset the natural buoyancy of your body and your wetsuit so you can descend.

Add a mask (so your eyes can focus underwater), fins (to move efficiently) and an exposure suit (to stay warm), and you have a complete scuba kit. Each item is explained in detail in our scuba gear guides.

The one idea everything else rests on is pressure. Every 10 metres of seawater adds one atmosphere of pressure. At 10 m you are under twice the pressure you feel at the surface, and that affects your ears, your air consumption and the gas dissolving into your body. Scuba training is mostly about managing pressure safely, and that is why you should never dive without training.

The main types of underwater exploration

Scuba is only one of several ways to explore underwater. They differ in equipment, depth, training and risk.

Type	Breathing	Typical depth	Training needed	Best for
Snorkeling	Surface air through a tube	Surface, short dips	None (a briefing helps)	Anyone who can swim; families
Recreational scuba	Tank of air or nitrox	Up to 18 m (beginner) / 30–40 m (advanced)	Open Water course	Holiday divers, reef lovers
Technical diving	Several tanks, special gas mixes	Beyond 40 m, caves, deco dives	Extensive specialist courses	Very experienced divers
Freediving	One breath held	A few metres to 100 m+ (competition)	Freediving course recommended	People who want silence and minimal gear

Recreational scuba diving

This is what 95% of divers do and what this website focuses on. Recreational diving has clear limits. There is a maximum depth of 40 metres (and 18 m for new Open Water divers), no mandatory decompression stops (you can always swim straight up to the surface in an emergency, slowly), and there is always open water above you, so no caves or wreck interiors. Within those limits, recreational diving has an excellent safety record when people follow their training.

Technical diving

Technical ("tec") diving goes beyond those limits. Deeper dives, planned decompression stops, penetrating caves and wrecks, and gas mixtures such as trimix all need extra tanks, redundant equipment and a lot of specialist training. It is a fascinating discipline, but it isn't where anyone starts. Most tec divers have hundreds of recreational dives behind them.

Freediving

Freedivers explore on a single breath. It is quiet, graceful and needs very little gear, but it carries its own serious risk, especially shallow-water blackout. Freediving has its own courses and safety rules. Read our freediving introduction if you are curious.

Snorkeling

Snorkeling means floating face-down at the surface with a mask, snorkel and fins. It is the easiest way to see a reef and a great first step if you are unsure about scuba. On shallow reefs you often see nearly as much as divers do. See our snorkeling guide.

What does scuba diving feel like?

Most new divers describe two surprises. The first is how quiet it is. You hear your own breathing and the bubbles, and little else. The second is weightlessness. Once your buoyancy is right, you hover in mid-water without effort, which feels a lot like flying. Fish often ignore you as long as you move slowly. Our article on what your first dive feels like goes into more detail.

It is also normal to feel a little strange at first. Breathing through your mouth only, the taste of dry compressed air and the pressure on your ears all take a few minutes to get used to. Almost everyone settles in within the first dive.

Is scuba diving dangerous?

Scuba diving has real risks, but they are well understood and largely preventable. The most serious problems, such as lung over-expansion injuries, decompression sickness and running out of air, are almost always linked to breaking basic rules: holding your breath while ascending, going up too fast, diving deeper or longer than planned, or ignoring your air gauge. Good training, a reliable buddy, a dive computer and conservative habits remove most of the risk.

Where scuba diving can take you

With a basic certification you can dive almost anywhere in the world. That includes coral reefs in the Red Sea and Thailand, crystal-clear Mexican cenotes (with a guide), historic wrecks in the Mediterranean, and kelp forests in cooler seas. Many divers plan their holidays around diving once they start.

How to get started

1. Check you are fit to dive with the standard medical questionnaire.
2. Try it with a Discover Scuba (try-dive) session. It usually takes half a day, no certificate needed.
3. Get certified with an Open Water course, which typically takes 3–4 days.
4. Keep diving regularly to build skill and confidence.

Frequently asked questions

What does SCUBA stand for?

SCUBA stands for Self-Contained Underwater Breathing Apparatus. The term was popularised in the early 1950s. Today "scuba" is used as an ordinary word.

Do you breathe oxygen when scuba diving?

No. Recreational divers normally breathe ordinary compressed air (about 21% oxygen and 79% nitrogen). Some certified divers use enriched air nitrox, which has a bit more oxygen. Pure oxygen is toxic at depth and is not used for normal diving.

How deep can a beginner scuba dive?

A try-dive is limited to about 12 metres. A newly certified Open Water diver may dive to 18 metres, and an Advanced Open Water diver to 30 metres. The recreational limit is 40 metres.

Is snorkeling the same as scuba diving?

No. Snorkelers stay at the surface and breathe through a tube, while scuba divers carry a tank and can stay underwater for an hour. Snorkeling needs no certification; scuba does.