There are some older, less starlette-like women who break the mold (especially if they are in authority), but Dea's point is one I had not considered in this context, & deserves more thought.
Diving is not the only place, of course that the presence of an older woman breaks the sexy image of the activity. In my art classes, for example, the middle-aged ladies are immediately written off as aimless retirees trying to fill lonely hours by doing bad portraits of their grandchildren, while the youthful males are treated as potential hot-shot illustrators. The instructors create self-fulfilling prophecies in many cases, leaving the ladies to languish over frustrating design problems while jovially indulging the boys with lots of hands-on advice. It does my heart good to see "Granny" get a hot job with a big studio! (Althought there are the occasional stereotypical grannies who demand way too much time in class, lowering the overall professional focus.)
In recreational diving, most OW students won't make their careers in the sport, but are the teachers showing more interest in potential peers & protogee's? Instructors vary in age & sex, but I would be interested in how many of either sex or any age choose to focus on the jocular young men? They have a lot of energy & are impossible to ignore. (This has been proven in school classrooms) Does the presence of a "mom" make boys feel uncomfortable about cussing & telling dirty stories? Does the whole group feel responsible for protecting her? Does everyone presume she will be slow & clumsy & hold them all back? Is there a cultural indocrination with women over 35 that makes us seem overly questioning & tentative to younger men?
It seems there are more layers to subtle discrimination than I had thought. We can't force people to change their gut reactions, but if we unerstand them, we can perhaps learn to work around them or thru them. Keep 'em coming!