PADI vs SSI vs NAUI: Which Agency Is Best?

Shop around for a learn-to-dive course and you will soon meet agency names: PADI and SSI above all, plus NAUI, RAID, SDI and CMAS. The choice matters less than the marketing suggests. The main agencies build their entry-level courses to published minimum standards, and the card you walk away with lets you hire gear, get tanks filled and dive with a buddy at dive operations around the world.

This guide compares the agencies using their own published standards, explains how the cards line up, and shows which agencies the dive shops in the ScubaDownUnder directory teach.

The short answer

- PADI, SSI and NAUI entry-level courses each include at least four open water dives and train you to a maximum of 18 metres. - Agencies accept each other's entry-level cards for their next course, so you can switch later. - The instructor and the school make far more difference to how well you dive than the logo on the card.

What a certification agency does

An agency writes the training standards, certifies instructors, supplies course materials and issues your certification card, usually called a C-card. The dive centre and its instructors deliver the course under that agency's rules.

The Recreational Scuba Training Council (RSTC), whose members include PADI, SSI, RAID and SDI, sets out what the card is for: a certified open water diver can buy air, hire equipment and plan and make dives with no decompression stops alongside another certified diver, without supervision.

PADI, SSI and NAUI side by side

| | PADI | SSI | NAUI | |---|---|---|---| | Founded | 1966 | 1970 | 1959 | | Entry course | Open Water Diver | Open Water Diver | Open Water Scuba Diver | | Minimum age | 10 (Junior to 14) | 10 | 10 (Junior to 14) | | Open water dives | 4 | 4 | At least 4 | | Depth limit | 18 m | 18 m | 18 m in training | | Theory online | PADI eLearning | MySSI app | NAUI online courses | | Standards | RSTC member | RSTC founding member, ISO 24801-2 | ISO 24801-2 |

PADI: the biggest network

PADI, the Professional Association of Diving Instructors, was founded in 1966 by John Cronin and Ralph Erickson. By its own count it has certified more than 30 million divers, has about 6,600 dive centres and resorts and 128,000 professional members, and it calls itself the world's largest dive training organisation.

Divers aged 10 to 14 earn a Junior Open Water card, which becomes a full Open Water card automatically at 15. After pool sessions (confined water training) you make four open water dives, and the card qualifies you to 18 metres.

PADI sells the theory as eLearning, bought direct or through your dive centre. PADI says that fee covers the theory only, and the dive centre charges separately for pool and open water training and gear hire, so compare total prices. PADI also supports referrals: theory and pool work at home, open water dives with another PADI centre while you travel. Start E-learning here

SSI: learning through one training centre

Scuba Schools International was established in 1970. It describes itself as the world's largest professional business-based training agency, with more than 4,000 training centres and 100,000 professionals in over 150 countries. SSI says it was a founding member of the RSTC, and its Open Water Diver course is certified to ISO 24801-2, the international standard for an "autonomous diver" (someone trained to dive with a buddy, without an instructor).

SSI's standards list six theory sessions, six pool sessions and four open water dives, a maximum training depth of 18 metres and a minimum age of 10. Every student must choose an SSI training centre as their training partner. Materials, your digital card and logbook live in the free MySSI app, and SSI says each centre decides whether materials, tuition, dives and certification are charged separately or as a package. That is the practical difference from PADI: with SSI you usually buy everything through the centre.

NAUI: the not-for-profit with instructor freedom

NAUI, the National Association of Underwater Instructors, is a not-for-profit association incorporated in Florida. It grew out of the National Diving Patrol, which took the NAUI name in 1959, and its motto is "Dive Safety Through Education".

NAUI grants its instructors what it calls academic freedom: they may teach in any reasonable way as long as NAUI standards are met, and may exceed them, for example by adding open water dives or theory. How much that helps depends on the instructor.

The entry course, Open Water Scuba Diver, is written to ISO 24801-2. NAUI's 2026 standards set an adult minimum age of 15 (Junior from 10 to 14), at least four open water dives, 18 metres maximum during the course, and an estimated 14 hours of theory plus 17 hours of practical training, at least 10 of them in the water. Online courses and a digital card come through NAUI's member platform and app. To find NAUI training in Australia, use NAUI's own dive centre locator, because our directory can only record PADI or SSI.

PADI alternatives: RAID, SDI, CMAS and BSAC

RAID. RAID's Open Water course runs from age 10 (Junior to 14) to a maximum of 18 metres. Its FREe-Learning platform lets you download the manuals and do the quizzes before you sign up with a RAID dive centre. RAID says it teaches buoyancy, trim and gas planning from the first course rather than as later specialties. It belongs to the RSTC in the US and Europe and has an Australia and South Pacific regional office.

SDI, with TDI. Technical Diving International (TDI) was founded in 1994, and Scuba Diving International (SDI) followed in 1998 as its recreational arm. SDI says it was the first agency to let students learn using a dive computer. Its Open Water Scuba Diver standard requires at least four open water dives to 18 metres, with Junior certification from 10 to 14. The link to TDI suits divers heading for technical diving, which TDI defines as dives involving decompression, extra cylinders, other gases, rebreathers or overhead environments such as caves.

CMAS. The World Underwater Federation (Confédération Mondiale des Activités Subaquatiques) was founded in Monaco in 1959 with Jacques-Yves Cousteau as its first president. It is a federation of national bodies in more than 130 countries, its diver grades use stars starting with One Star Diver, and CMAS says its certificates are recognised worldwide.

BSAC. The British Sub-Aqua Club is a UK body built around local clubs, worth knowing if you learnt in Britain. Its entry course, Ocean Diver, starts at 12, qualifies divers to 20 metres rather than 18, and includes nitrox (air with extra oxygen) up to 36 per cent.

Will an operator accept my card?

In practice, yes, from any of these agencies, although no single body guarantees it:

- Shared minimum standards. The World Recreational Scuba Training Council (WRSTC), founded in 1999, coordinates minimum course standards through councils in the US, Europe, Canada and Japan. PADI, SSI, RAID and SDI are listed members. NAUI is not, but its course is built to the ISO standard. - An international standard. ISO 24801-2 defines what an autonomous diver must be able to do, and Australia adopted it word for word as AS ISO 24801.2:2021. - Australian law uses the standard, not brand names. Queensland's Safety in Recreational Water Activities Regulation 2024 defines a certified diver as someone certified by a training organisation whose training substantially complies with AS ISO 24801. It names no agency. - Agencies accept each other. PADI's Advanced Open Water course accepts a qualifying certification from another agency, NAUI's continuing courses accept its Open Water card "or the equivalent", and CMAS offers crossovers. Our PADI course levels guide maps PADI's ladder to SSI's.

An operator may still ask for your logbook or recent dives before a demanding site. That is the sign of a careful operator, not a problem with your agency.

Which agencies Australian dive shops teach

The ScubaDownUnder dive shop directory listed 124 Australian dive shops on 13 October 2026. Each listing has one agency field, which can hold PADI or SSI:

| State | Shops | PADI | SSI | Not recorded | |---|---|---|---|---| | Queensland | 39 | 24 | 8 | 7 | | New South Wales | 25 | 12 | 5 | 8 | | Western Australia | 21 | 8 | 3 | 10 | | Victoria | 19 | 9 | 3 | 7 | | South Australia | 11 | 6 | 0 | 5 | | Tasmania | 6 | 4 | 0 | 2 | | ACT | 2 | 1 | 0 | 1 | | Northern Territory | 1 | 1 | 0 | 0 | | Total | 124 | 65 | 19 | 40 |

Three caveats. This is our directory, not a census of Australian dive shops. It records one agency per shop, so a centre teaching both PADI and SSI appears under only one. And "not recorded" means the field is blank: the shop may teach NAUI, RAID, SDI or another agency the field cannot hold, may not run courses, or we may not have recorded it yet. It does not mean the shop teaches neither.

Even so, the pattern is clear: of the 84 shops with an agency recorded, 65 (about three in four) are PADI, and PADI is the most recorded agency in every state and territory. SSI shops appear in Queensland, New South Wales, Western Australia and Victoria, with none recorded in our South Australian, Tasmanian, ACT or Northern Territory listings. Of all 124 shops, 100 list courses among their services, and you can filter the directory by state, agency and service.

How to choose a dive school

Because every Open Water course covers the same core, the school is where the real differences lie. Before you book, ask:

- Who will teach me, how long have they been instructing, and can I meet them first? - How many students will each instructor have in the pool and in the ocean? - Where are the open water dives, and what happens if the weather turns? - What does the price include: eLearning, certification fee, gear hire, boat fees? Our guide to how much it costs to get scuba certified breaks these down. - What do recent students say in their reviews?

If you are still deciding where to learn, our guide to where to get scuba certified in Australia compares Cairns, Sydney, Melbourne and Adelaide.

Which agency should you choose?

For most Australians the honest answer is to choose the school first, then accept whichever agency it teaches. The core skills are the same, operators worldwide accept the cards, and you can change agency at the next level. A few situations tip the balance:

- You want the most choice of schools, here and overseas. PADI has the largest network by its own figures, and it dominates our directory. - The school you like best teaches SSI. Take it. Its Open Water card is built to the same ISO standard. - You have found a NAUI instructor you trust. Academic freedom lets a good one shape the course around you. - You are curious about technical diving. SDI shares a family with TDI, and RAID also runs technical and rebreather courses.

A brilliant instructor from any of these agencies will teach you more than a mediocre one from the biggest.

Ready to start?

PADI eLearning lets you begin your Open Water theory online at your own pace, then complete your pool and ocean dives with a local PADI dive school when you're ready.

Begin your diving journey

Sources

- PADI: About PADI - PADI: Open Water Diver course - PADI: Advanced Open Water Diver course - SSI: About SSI - SSI: Open Water Diver certification - SSI: MySSI app - NAUI: Our Heritage - NAUI: Frequently asked questions - NAUI: Open Water Scuba Diver (Autonomous, ISO Level 2) - NAUI: Standards and Policies Manual, 2026 edition (PDF) - RAID: Open Water - RAID: Continue learning with RAID - RAID: Regional contacts - SDI, TDI, ERDI and PFI: Our story - SDI: Open Water Scuba Diver standard (PDF) - CMAS: About CMAS - CMAS: Scuba diving (air) programmes - CMAS: Frequently asked questions - BSAC: Ocean Diver beginner course - WRSTC: Mission statement - WRSTC: United States Council members - WRSTC: Minimum course content for Open Water Diver certification (PDF) - ISO: ISO 24801-2:2014, Recreational diving services, Requirements for the training of recreational scuba divers, Part 2: Level 2, Autonomous diver, iso.org - Standards Australia: AS ISO 24801.2:2021 - Queensland Legislation: Safety in Recreational Water Activities Regulation 2024 - ScubaDownUnder: Dive shop directory, agency data as at 13 October 2026

Header photo: A buddy pair of divers recording reef data for Reef Check Australia over branching coral on the Great Barrier Reef, March 2008, by Steveprutz, CC BY 3.0, via Wikimedia Commons.