DevonDiver
N/A
...practices not currently taught by mainstream agencies....concepts like deep air, independant doubles, solo, deco light, yada yada.
Deep Air - taught up to 50m. 'Alternative' would be dives beyond 50m, for most agencies.
Independent Doubles - taught.
Solo - taught.
Deco light - taught.
Other than 50m> air dives, this is all pretty mainstream.
The only thing 'alternative' is doing on the basis of internet discussions, rather than a comprehensive training course.