The British Sub-Aqua Club or BSAC has been recognised since 1954 by UK Sport as the national governing body of recreational diving in the United Kingdom.

The club was founded in 1953 and at its peak in the mid-1990s had over 50,000 members declining to over 30,000 in 2009. It is a diver training organization that operates through its associated network of around 1,100 local, independent diving clubs and around 400 diving schools worldwide. The old logo featured the Roman god Neptune (Greek god Poseidon), god of the sea. The new logo, as of 2017, features a diver with the updated BSAC motto "Dive with us".

BSAC is unusual for a diver training agency in that most BSAC instructors are volunteers, giving up their spare time to train others, unlike many other agencies, in which instructors are paid employees, or self-employed.

Given that UK waters are relatively cold and have restricted visibility, BSAC training is regarded by its members as more comprehensive than some. Specifically it places emphasis on rescue training very early in the programme. BSAC also maintains links with other organisations, such as NACSAC.

It has been recognized since 1954 by the Sports Council as the national governing body of recreational diving in the United Kingdom whose principle activity is to promote underwater sport, exploration and science and related studies, safety in those activities, and the highest standards of training, education and participation.

The number of BSAC members saw a significant increase from 1965 to 1995, where it reached a maximum of 52364 members. Since 1995 the number of members has shown a consistent decline to only 27,000 members in 2019. However, it is still the largest diving club in the world. 

According to statista & wikipedia