PADI vs SSI vs NAUI vs BSAC what are the differences. There are a number of differences between the scuba diving agencies. Starting with PADI, they would be considered as a ‘training agency’ trading for a profit. Compared to BSAC at the other end of the scale would consider itself to be more of a ‘club’, and is a non-profit organisation. SSI is similar to PADI, as it’s also a profit making dive organisation, whereas NAUI is similar to BSAC, as it is also a not for profit scuba diving organisation.