On commercial ships, I doubt there's any full-time IT position since they really try to go almost crewless in order to keep costs to the bone. On cruise lines--you are looking at something arguably worse: A combination of the 'hospitality industry' and shipping, each of which generally believes that pond scum can be whipped into working harder and for less money, and easily replaced if they object. A lot like corporate IT in many ways--but you don't get to go home at night, you get a bunk bed in a shared cabin, indoors, below decks, with instructions not to fraternize with the paying passengers.
I think you'd do better to try finding a job in corporate IT in one of the fields that pays well (security, etc.) or possibly in casino security operations (and then moving to a shipboard casino, since security has some limits to hours and some extra pay) in a shop that is big enough to have shifts, so you get time off--when you can take some of that hard-earned pay and go sailing on your own with it.
A lot of corporate IT shops want 20 year olds with 20 years of experience, willing and outright eager to work 80 hour weeks at 40 hour pay. Those are the shops that will promise you lots of excitment and growth--and burn you out fast. Interview them, and screen them, agressively to avoid getting stuck in one.