Copyright PADI 2012
I got into photography through underwater photography in the late 1970s. Since then, there have been two major innovations for shooting underwater: digital, and closed-circuit rebreathers (CCRs).
Digital imaging eliminated the limit of 36 photos before you have to surface, open the housing and reload the camera. In that era, I sometimes worked with an assistant on the boat to whom I would hand the housing. The assistant would rinse it, open it, pull out the camera and exchange it for another one (identical model) with a fresh roll in it, then reseal it. While I shot the next roll, he unloaded and reloaded the camera.
On my first production shoot with a digital camera, I did on a dive what used to take a day.
With digital imaging, UW shooters are limited to their life support -- how long their air lasts and other limits. With conventional scuba using as single cylinder, this means you have no more than an hour -- typically less. More recently, serious divers are using CCRs, which recycle your breathing gases and optimize the oxygen-nitrogen ratio. Without getting into technical details, with CCRs, dives of two or three hours aren't unusual. The image above was taken on a 2+ hour dive while on location in Grand Cayman.
My first production shoot with a CCR repeated the experience I had when I switched to digital: I did in a dive what used to take a day. I estimate that with respect to underwater shooting, using the combination of digital/CCR (assuming your models are using CCRs) we have an efficiency factor of around 9. That is, we do in one dive what used to take us 9 dives in the film era.