Scuba Certification Comparison: PADI vs SSI vs CMAS vs NAUI Course Equivalents

Do the course levels really match?

Broadly, yes. Most major agencies follow standards set or influenced by the WRSTC (World Recreational Scuba Training Council) and ISO 24801, which define minimum skills for three recreational levels:

ISO level	Meaning	Typical courses
ISO 24801-1 "Supervised Diver"	Can dive to 12 m under professional supervision	PADI Scuba Diver, SSI Scuba Diver
ISO 24801-2 "Autonomous Diver"	Can dive with a buddy to 18–20 m	Open Water Diver (PADI/SSI), NAUI Scuba Diver, CMAS ★
ISO 24801-3 "Dive Leader"	Can lead dives and plan for others	Divemaster, CMAS ★★★ (in many federations)

That's why dive centres around the world accept each other's certifications. Your experience (number of dives, last dive date, types of diving) often matters more than which card you hold.

Key differences in practice

• Availability: PADI and SSI are found in almost every holiday destination. CMAS and BSAC are strongest in European clubs. NAUI is most common in the USA.
• Materials: PADI charges for its learning materials; SSI's digital materials are often free through a centre.
• Flexibility: NAUI and SSI give instructors somewhat more freedom in skill order; PADI is highly standardised.
• Community: club-based systems (CMAS, BSAC) come with ready-made buddies and regular club dives.

For a detailed look at each agency, read PADI vs SSI vs CMAS vs NAUI.

The most important factor

Whatever agency you choose, the quality of your training depends mainly on your instructor and dive centre: group sizes, pool time, patience and safety culture. Use our dive centre checklist before you book.

What each level lets you do

Level	You can…	Typical requirement
Entry (Open Water / ★)	Dive with a certified buddy to 18 m, rent gear, get tank fills, join guided fun dives	No experience needed
Advanced (AOW / ★★)	Dive to 30 m, join most liveaboards and deeper sites	Entry certification
Rescue	Manage emergencies, assist other divers	Advanced + first aid/CPR
Divemaster / ★★★	Lead certified divers, assist instructors, work in diving	Rescue + 40–60 logged dives

Switching agencies later

You're never locked in. Divers routinely do Open Water with one agency and Advanced with another. Dive centres simply check your card and logbook. Some agencies offer formal crossover programmes for professionals (Divemasters and instructors) who want to teach with a different organisation.

A few practical tips:

• Keep a digital copy of every certification card (most agencies have apps)
• Log every dive, including training dives. Experience is what dive centres care about most
• If you lose a card, request a replacement from the issuing agency
• Specialty courses (nitrox, deep, wreck) are generally recognised across agencies too

Frequently asked questions

Is SSI Open Water the same as PADI Open Water?

They are equivalent entry-level certifications, both allowing you to dive with a buddy to 18 m, and they're accepted worldwide.

What is the CMAS equivalent of PADI Open Water?

CMAS One Star Diver (★) is broadly equivalent to Open Water, although requirements vary between national federations.