I'd speak with Frank Wasson, Captain of the Spree in Key West & TX Flower Gardens. He's Wookie on SB. He runs his own operation from marketing, booking, etc. Maybe take one of his trips.
I'd also second the comment about working on a boat for a while. Make your mistakes on someone else's dollar.
Unless you're independently wealthy and ready to squander a good bit of it, the fact that you're even asking the questions says you're not ready. From someone who has started three businesses from scratch.
Maybe you'll listen to Frank more than Frank listened to me...??
I think it's a bit much to say someone's not ready to make the plunge into something like this simply because they're asking for (and hopefully listening to) input. But if you're new in the diving business, and/or haven't started up your own business, you'll be on a steep learning curve that in 95%+ of all cases takes lots of cash to keep up with. You're going to make mistakes, and your mistakes will cost you money. If you don't have the money, then one mistake may well shoot you in both feet. And of course boats, and all their associated high-dollar equipment, suck money at a prodigious rate, no matter how complex and complete and impressive your spreadsheets are.
The diving industry is a relatively small industry - the dive travel business is even smaller, and the liveaboard dive travel industry is a small subset of even that. Most of us know each other at least in passing. That means that being successful in this business requires some degree of politicking in order to successfully run the operation, because you're going to need others' help, input and advice. Filling the boat with paying guests is another story, and is another area in which success depends in many cases on who you know, and how successfully and for how long you've spent your marketing dollars to hammer people over the head and tell them that you're out there, available for charter, and have stuck it out long enough that (a) you know what you're doing and (be) you're trustworthy.
If you can keep up with all of the above, then think about whether you want to make your passion into your business, and have your passion all of a sudden be the source of all the stress and heartache and WORK in your life.
If you're good with that, then think about how good you are listening to others. If you're a long-time liveaboard diving aficionado, you know exactly how it should be done RIGHT - right? I flat-ass guarantee you that you're wrong - because on any boatload of people, others (and if you start a liveaboard, these'll be the ones that pay you to be there, establish your reputation, and tell others about your operation) will disagree with you on some material aspect of how you do what you're doing - even when they have far less experience. You have to know how to listen to others - your crew, guests, agents, etc - and keep learning how to do it better, because at the end of the day they're the ones that are keeping you in business in one way or another.
I'm not saying it can't be done, and I'm not saying don't do it - certainly the business has its rewards. But it's a capital-intensive, low margin business in the best of times, even when you successfully navigate lots of treacherous waters. You have to go into it with your eyes open, and no matter what I or anyone else tells you, be prepared for the feeling that no one was able to pry your eyes open even close to wide enough.
Good luck if this is what you choose to do!
- Clay