According to the certifications added by scuba divers on DiveBuddy.com, the following list indicates the percentage market share by each certification agency. Only the unique certification agencies were counted for each diver. For example, if a diver listed 3 different certifications with PADI and 1 for DAN, the list below includes 1 for PADI and 1 for DAN. All types of certifications were included (entry, advanced, tech, recreational).
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Sample size: 3747 unique scuba divers that listed their certifications
PADI: 55.60%
SSI: 10.53%
NAUI: 10.14%
SDI: 4.96%
TDI: 3.13%
DAN: 2.05%
IANTD: 1.63%
Red Cross: 1.16%
NASE: 0.89%
CMAS/WUF: 0.87%
YMCA: 0.81%
NASDS: 0.57%
NSS/CDS: 0.53%
PDIC: 0.51%
IDEA: 0.47%
Other: 6.16%