Most of my videos are in the 30-60 min range, at least the ones for my cable TV show and commercial DVD's. My interest is in telling a story, although that story focuses on the marine life itself and its biology, ecology, behavior. I use divers in my videos occasionally, usually to indicate transitions to other subject matter.
I've just started producing a few shorter videos (1-15 min) and even with these I have the same kind of story to tell since my primary goal is education.
I must admit when I watched one of Howard and Michelle Hall's "latest" IMAX films, I was very disappointed at the amount of topside story interjected into the underwater footage. I'm sure for some, especially non-divers, it made the story more interesting. However, I found some of it too contrived for my tastes. Of course their underwater footage was great!
Then some divers who have viewed my DVD's and TV show have suggested I insert more of myself as the "charismatic guide and personality" into my stories. I may do a little of that in my future Kelp Forest Ecology series, but I've always preferred to be off-screen rather than on-screen! Hmmm, I really should use my lovely lady dive buddies instead.