RJP,
Hypothetically speaking, if you were given the job to mass market scuba diving and increase the volume of divers and worldwide, no budget, no rules, everything on the table, as many people and resources as you need but you are the man solely responsible to make this happen,
how would you do it?
Faulty premise.
I wouldn't "mass market" scuba diving, because it's not a "mass market" product. Toilet paper and sneakers and soft drinks are mass market products. Scuba diving is a "niche" product.
Besides that, the idea of asking what I would do if there was "no budget, no rules, everything on the table, as many people and resources as you need" is so absurd that it actually makes the question harder to answer rather than easier. It's like asking an engineer what they would do to improve automobile fuel efficiency... assuming the laws of physics were suspended.
As an example of what I might do if I had "no budget, no rules" to promote diving, I would pay every person in the world over the age of fourteen $1,000 to attend a Discover Scuba Program. You gotta figure some of those people will actually find out that they like diving, and end up pursuing the sport. And, each of those people would have $1,000 in hand to pay for certification and some gear.
:d
But seriously, the answer to your question is that marketing is not about having the answer, but rather about knowing how to find the answer. That's what people like me do. We don't HAVE the answers, we simply know how to FIND them.
Step one - figure out what the current issue is: "Why don't more people dive?" Anyone who says they know the answer - without having done adequate, well-controlled market research - is simply making s--t up, and shouldn't be listened to. (Hint: people already in the industry are the least likely to already know the answer. As proof of this, I'll offer the fact that they haven't solved the problem yet.)
Step two - figure out which segment of people who don't currently dive can actually be motivated to do so. Some can't. Move on.
Step three - of those who CAN be motivated to dive, determine which segment(s) can be most efficiently reached (budget, resources, rules, etc being a reality). Suppose you discovered that the Amish, American Indians, and people who lived more than 100mi from a scuba training facility were most interested in diving? Their media consumption habits make it nearly impossible to target them with your message. Suppose you found that NYC was a great market? Media and promotion costs in NYC are crazy expensive. A market of a quarter the potential in Cincinnati or St Louis is far more cost effective to reach.
Step four - if you want to be really good, you'd go the extra step further and figure out which segments will a.) pay the highest prices for training, b.) buy all their own gear, c.) dive locally and/or travel multiple times per year to dives, and d.) stay with the sport the longest over time.
Step five - craft a motivating message to get our identified audience to take action; this is not about getting a celebrity to say "everyone should try diving" because nobody know's who everyone is, much less thinks they are part of "everyone." As a made up example, suppose we found a large segment of the population were HOH (head of household) with 2+ kids who feel like their families are all going their seperate ways and are craving some sort of thing they could all do together? You can imaging that the message to them would be very different than if we determined the best target audience was empty nesters looking to get out of the house now that they have the freedom of their kids being gone. Compare that to the potential message if the target audience was single 25-34yr old males looking for adventure and hot chicks?
Step six - determine the tactics and media to reach our target audience with our message. Channel and media selection vary greatly depending on target demographics, and are often very counter-intuitive. (eg, we have a client who's target audience is largely indigent. Would you try to reach them via TV, print, or a smart-phone enabled website? Turns out that most indigent people in this group don't have TVs... but they do have web-enabled smart phones.) We've got media/channel planners that can figure out how to reach 6'2" left-handed Hispanic lesbians... if that's your target audience.
But even those steps would vary depending on the objectives. Do you want the industry to create more divers, or to make more money? Two very different things. Think about Timex vs Rolex? Which one sells more watches? (It's not even close.) Which one makes more money? (It's not even close.) In my absurd example above (Paying people to take a DSD) I would refine the rules of that approach significantly depending on whether your objective was volume or profitability. (eg. I might limit participants to those people who lived in zip codes where the mean household income is at least 10x the federal poverty level, in order to ensure that those who discovered they liked diving could actually afford to do so.)