C-card

The certification card proving a diver's training level, checked by dive shops and operators before renting gear, filling tanks, or taking you diving.

A C-card, short for certification card, is the credential that proves you completed a scuba course. Dive operators check it before renting you equipment, filling your cylinders, or taking you on a boat, and they match the card's level against the planned dive: an Open Water card for a 30 m wall dive will usually get you politely reassigned to a shallower site.

The card shows your name, certification level, agency, certification date, and often your instructor's number. Cards do not expire, although after long inactivity operators commonly ask for a refresher course or a check dive. Most agencies now issue digital cards through their apps alongside or instead of plastic, and a lost card can be replaced by the agency since your certification lives in their database, not in the plastic itself.

Bring your card, or have the app ready, whenever you travel to dive. Operators may also ask to see your logbook to judge recent experience, since the card proves training level but says nothing about how recently you used it. Higher level cards, such as advanced or rescue ratings, unlock deeper sites and some demanding trips, so divers often carry proof of every level they hold.