If someone did use sidemount in open water before Steve Bogaerts nobody knew about it.
Steve himself is using it for 'extreme cave exploration' he doesn't count.
Lamar always marketed to cave divers, judged by his videos he seems never to have thought about open water applications except cavern.
Steve Martin more or less 'pioneered' worldwide sidemount adoption outside caves, in my opinion.
And instructors without challenging caves close by like Andy Davis, Garry Dallas and Tom Steiner took it forward from that point in the last few years only.
Steve himself is using it for 'extreme cave exploration' he doesn't count.
Lamar always marketed to cave divers, judged by his videos he seems never to have thought about open water applications except cavern.
Steve Martin more or less 'pioneered' worldwide sidemount adoption outside caves, in my opinion.
And instructors without challenging caves close by like Andy Davis, Garry Dallas and Tom Steiner took it forward from that point in the last few years only.