Belzelbub
Contributor
I voted for SPG, PDC, and BCD. All three of those altered how dive training was done. Training is no longer done with J valves, though their existence may be mentioned as a historical note.
Likewise, the BCD has become a huge part of training. There are also now several specialized types of BCDs for personal preference or specialized diving.
When I was first certified, dive computers were mentioned, but they weren’t in wide use. We did the training using tables. Computers were only mentioned. IIRC, my first instructor saw them as a tech tool and unnecessary for recreational diving. That has flipped in training. Now, much more time is spent on the PDC, tables might be introduced, but most likely not used much in the course.
Likewise, the BCD has become a huge part of training. There are also now several specialized types of BCDs for personal preference or specialized diving.
When I was first certified, dive computers were mentioned, but they weren’t in wide use. We did the training using tables. Computers were only mentioned. IIRC, my first instructor saw them as a tech tool and unnecessary for recreational diving. That has flipped in training. Now, much more time is spent on the PDC, tables might be introduced, but most likely not used much in the course.