C-card is the generic term for any certification

Certification

Certification refers to the confirmation of certain characteristics of an object, person, or organization. This confirmation is often, but not always, provided by some form of external review, education, assessment, or audit...

 card issued by a recognized scuba diving

Scuba diving

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

 instruction organization, such as PADI

Padi

Padi or PADI may refer to:* Padi, Chennai, India* Padi , a musical group* Paddy field, a type of cultivated land * Professional Association of Diving Instructors, a scuba organization...

 or SSI

Scuba Schools International

Scuba Schools International or SSI is an organization that teaches the skills involved in scuba diving and supports Dive Businesses and Dive Resorts.SSI has well over 2,500 authorized dealers and 35 Regional Centers and Area Offices all over the World....

. While usually taken to mean the minimum level training required to dive safely, it also applies to advanced certifications in a general manner.

A typical card will list:

• Certifying organization
• Name and photograph of the person certified
• Certification number
• Type of certification (basic, open water, advanced, nitrox, probationary, special skill, etc)
• Date of certification
• Name of instructor
• Instructor's certification number

As a general rule, dive shops worldwide will demand to see a C-card before filling air cylinders or allowing a person to participate in a dive. This is done not only to minimize the risk to the diver, but to minimize the potential legal liability to the dive shop.