PADI vs SSI vs CMAS vs NAUI: Which Scuba Certification Should You Choose?

When you start looking for a scuba course, you'll see a jumble of acronyms: PADI, SSI, CMAS, NAUI, BSAC, RAID, SDI. These are training agencies. They write the course standards and training materials, certify instructors, and issue certification cards. They don't usually run the dive centres themselves; independent dive shops affiliate with one or more of them.

The short answer

For a beginner, all major agencies teach the same core skills to broadly similar standards, and their entry-level certifications are accepted by dive centres worldwide. Most agencies are members of the WRSTC (World Recreational Scuba Training Council) or follow ISO 24801 standards, which set minimum requirements for entry-level training. Choose the instructor and dive centre first and the agency second.

Quick comparison

	PADI	SSI	CMAS	NAUI
Founded	1966, USA	1970, USA	1959, France (world federation)	1960, USA
Entry-level course	Open Water Diver	Open Water Diver	One Star Diver (★)	Scuba Diver
Max depth after entry course	18 m	18 m	Typically 18–20 m (varies by federation)	18 m
Presence	Largest worldwide, everywhere	Very large, especially Asia and Europe	Strong in Europe, clubs and federations	Strong in USA, smaller abroad
Learning materials	Paid e-learning or manual, required	Digital materials often free via the centre	Varies by national federation	Manual or e-learning
Teaching style	Highly standardised, modular	Standardised, flexible skill order ("Diver Diamond")	Club-based, often longer and more theory	Instructors have more flexibility
Recognition	Universal	Universal	Very wide	Very wide

Want an interactive version? Use our certification comparison tool.

PADI (Professional Association of Diving Instructors)

PADI is the world's largest training agency, and you'll find PADI dive centres in almost every diving destination. Its courses are highly standardised: an Open Water course in Egypt follows the same structure as one in Mexico. PADI's e-learning is polished, and its course ladder (Open Water → Advanced → Rescue → Divemaster) is the one most people know.

SSI (Scuba Schools International)

SSI is PADI's main competitor and extremely popular in Southeast Asia, the Red Sea and Europe. SSI courses are usually taught through a specific dive centre, and digital learning materials are often included free. Standards and skills are very similar to PADI's, and many instructors teach both.

CMAS (World Underwater Federation)

CMAS is an international federation of national diving organisations, many of them non-profit clubs. It uses a star system: One Star (★), Two Star (★★), Three Star (★★★). CMAS training is common in France, Italy, Spain, Eastern Europe and parts of Africa and Asia. Club courses are often longer and cheaper, with more theory and a strong emphasis on self-rescue.

NAUI (National Association of Underwater Instructors)

NAUI is the oldest US recreational agency and is known for its motto "Dive Safety Through Education". It gives instructors more flexibility to adapt courses, and its training is widely respected. NAUI is most common in North America and less common in holiday destinations elsewhere.

Other agencies you might see

• BSAC (British Sub-Aqua Club): club-based UK training with a strong focus on cold-water diving and self-sufficiency.
• RAID: a modern agency with online-first training, growing in Asia and Europe.
• SDI/TDI: recreational (SDI) and technical (TDI) training; SDI teaches dive-computer use from day one.
• GUE: a highly standardised, performance-focused agency, popular with technical divers.

Are certifications recognised everywhere?

Yes, in practice. A dive centre in Thailand will accept your CMAS card, and a French club will accept your PADI card. What they check is your level (entry-level, advanced, rescue) and your experience (logged dives, date of last dive). Many agencies also have crossover programmes if you want to continue with a different agency later.

So which should you choose?

1. Choose the instructor. Small groups, patient teaching and good reviews matter more than anything else. See choosing a dive centre.
2. Consider where you'll dive. On holiday, PADI and SSI are the easiest to find. At home in Europe, a CMAS or BSAC club may offer great value and a ready-made group of buddies.
3. Compare total price, including learning materials, certification fee, equipment and boat trips.

Frequently asked questions

Is PADI better than SSI?

Not in terms of safety or skill. Both follow similar international standards for entry-level training. PADI is larger; SSI is often a little cheaper. The quality of your instructor matters far more.

Can I do Open Water with PADI and Advanced with SSI?

Yes. Agencies generally accept each other's entry-level certifications as a prerequisite for the next course.

Does my scuba certification expire?

No, recreational certifications don't expire. But if you haven't dived for 6–12 months or more, dive centres will usually ask you to do a refresher dive.