What are the differences between PADI and SSI scuba diving certifications?

PADI and SSI are both internationally recognized organizations that follow the safety standards set by the World Recreational Scuba Training Council, meaning both certifications are valid at any dive center worldwide. The primary difference lies in the teaching philosophy: PADI follows a standardized, step-by-step curriculum where skills must be mastered in a specific order, whereas SSI allows the activity provider more flexibility to adapt the sequence of skills to the pace of the participant. Additionally, SSI often includes digital learning materials within the course price and uses a store-based model where instructors are affiliated with a specific dive center. PADI is the more prevalent brand globally, though both systems are entirely interchangeable, allowing a diver to complete an entry-level course with one and advanced training with the other.