My wife and I are brand new to the sport, and as with everything we do, she worries about the money we spend. We can't afford this sport, but decided we would like to give it a go. We own things most 'can't afford', do things most would find cost prohibitive, but we can and do because we try and be smart about it.
I work as a salesman for pest & termite control. I hate it, and I probably make less than 90% of the employed folks here, and most likely less then the retired folks as well. My wife is a fulltime student, and we have an 8 year old daughter, and I pay child support for my son to my ex-wife. We are not living in the lap of luxury by any means.
We have zero debt. We rent a decent apartment, both drive older used cars that we paid $2k for each, we go out maybe once a month for dinners and a movie. We also have a boat that we paid $1k for.
How are we going to afford this sport is simple. I buy everything off Craigslist, eBay, or internet shops. I don't need the latest-greatest to be happy. We live in Florida, which I believe will afford us somewhat limitless diving opportunities without spending insanes amount of money.
I used to ski almost daily when I lived in Oregon, and like diving, it can be expensive to the point of bankruptcy if you get carried away. I don't let that happen.
As said before; it comes down to priorities. If you want a nice shiny new car, a fancy TV, and the prettiest of anything, it will cost you. I'm dumbfounded when I go to the marina and see $100k boats that haven't been used because the owners can't afford the fuel, and people who can't make their mortgage payment because they have too many toys they shouldn't have bought.
Don't use your credit cards (what are they?) to buy stuff you can't really afford. If you don't have the cash, you can't afford it. Keep sight of what you really want to do, and stay on target for it. It works. As I said, based on our household income, we can't afford the things we own and do, but because we budget and prioritize, we do it, and we have savings to boot.
Everything is expensive, if you let it be.