In 2005, out of a need to be in the water more, I added water and dive safety to my skills. I spent a few years establishing myself and now have a solid resume working with crew and talent on water sets. In 2010, I received my Padi Instructors Certification.
I work with actors in pre-production to decide if they should do scenes as scuba divers (using breathing apparatus), or if they should do them by holding their breath and coming to the surface for air.
Actors come with different levels of background experience and preferences for filming scenes underwater. Some are competent scuba divers and do not worry about doing their scenes using scuba apparatus, while others are less comfortable about putting the breathing regulator in and out of their mouth underwater in between shots.
Many actors come in without any scuba diving experience, and they might take to it right away, or might decide to pass, preferring instead to work on doing their scenes by breath holding.
Dive safety is one of my favorite jobs. Actor comfort level comes first, and my job is to figure out what they like, adjusting for that while getting the shot to work.
My underwater filming background gives me an advantage in figuring out how to make shots work without exerting the talent.