would I need a license to clean boat bottoms?
There is no licensing requirement to clean boat bottoms anywhere in this country. Washington does require that hull cleaners obtain a state permit, but that is the only place that is required, AFAIK
. A business license is a different matter. I service marinas in 5 or 6 different municipalities. Technically, I should have a business license in each, which could end up being a decent chunk of change for renewal each year. But I have been able to get by for 15 years with the one I keep current in the city in which my business is based.
Would people want me to be qualified to clean there boats?
SCUBA certification is meaningless. No boat owner gives a rat's ass about what level of recreational diving instruction you've attained. What they care about is if can you do the job they've asked you to do. Remember, diving is just the way we get to the job, like driving your car to get to the office. Diving is not the work, the work is cleaning the boat bottom and replacing zincs, among other things.
My only experince is cleaning my own boat and diving on a few vacations.
Every hull cleaner has to start somewhere. I get asked all the time if I'm hiring. I had a guy walk up to me in my garage yesterday, right off the street and ask me for a job (he's a certified SCUBA instructor). I'll tell you what I told him; I do hire divers but my personal preference is to hire divers who already have a hull cleaning business. Failing that, I want them to have some boating knowledge. Being able to dive isn't the important thing in this business. Knowing about boats and boat systems and having the temperment to be able to work on them underwater is the important thing. You've got most of that covered already.