What is the best way to get started as a marine vessel (yacht, cruise, merchant) engineer?

If you want to make this a career then I would go for the academy's. California Maritime is the easiest one to get into (I did..lol). Besides the degree you sail as an officer which pays ALOT more. The other way would be to go though one of the unlicensed unions. Here is that link http://www.seafarers.org/ Good luck and its a great job

I started out as a helper for a boat mechanic. I went to a tec. school. Marine technology. It was a two year course that went over all the systems of boats, plumbing, fuel systems, diesel engines, inboard/outboard, gas engines, outboard, etc.etc. I took that knowledge and went into the merchant marines. If you want to become a merchant marine I would not go to a vo-tech school, just go to school to become a merchant marine. As you upgrade you endorsements you go to class to learn the systems. There are some schools that are focused on becoming a merchant marine. You start at the bottom and work your way up. You still need to learn design and construction, if you don't know how it is made you can not fix the problem. There are pros and cons about both jobs. There is a whole bunch of info at Mother of all Marine links.

All deep sea US Flag merchant vessels are manned by union seafarers. Look into joining an union. They have their own engineering training programs.