Open Water Diver is an entry-level full diver certification

Diving certification

Diving certification is an award recognising a level of ability and knowledge in scuba diving. Divers carry a qualification record or certification card which is required to prove their qualifications when booking a dive trip, hiring scuba equipment or filling diving cylinders...

 for scuba diving

Scuba diving

Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....

. Although different agencies use different names, similar entry-level courses are offered by all diving agencies and consist of a combination of knowledge development (theory), confined water dives (practical training) and open water dives (experience). In the Professional Association of Diving Instructors

Professional Association of Diving Instructors

The Professional Association of Diving Instructors is the world's largest recreational diving membership and diver training organization founded in 1966 by John Cronin and Ralph Erickson...

 (PADI) system, the course is called Open Water.
The Sub-Aqua Association

Sub-Aqua Association

The Sub-Aqua Association or SAA is a diver training organization for scubadivers in the United Kingdom. The association and some other UK-based diving groups have traditionally used a club-based system with unpaid instructors, while the other principal training agency, PADI, organises most of its...

 (SAA) also offers a certification entitled 'Open Water Diver'. The SAA qualification is recognised by the Confédération Mondiale des Activités Subaquatiques

Confédération Mondiale des Activités Subaquatiques

The Confédération Mondiale des Activités Subaquatiques is the World Underwater Federation. CMAS is the international umbrella organisation for recreational diver training organisations represented in the CMAS Technical Committee and underwater sports governed by the CMAS Sport Committee...

 (CMAS) as a CMAS 1-star certification. The National Association of Underwater Instructors

National Association of Underwater Instructors

The National Association of Underwater Instructors is a non-profit 501 association of SCUBA instructors. It was officially CE and ISO certified in May 2007 in all three diver levels and both instructor levels.-History:...

 (NAUI) entry-level course is called Scuba Diver.
The British Sub-Aqua Club (BSAC) calls its equivalent qualification 'Ocean Diver'.