There has been a craps table on every Carnival ship I have been on (Ecstasy, Fantasy, Paradise, Pride and Inspiration). Pretty sure there is a craps table on every Carnival ship. The minimums I have seen are always $5.00, though I did see one time where they had $3.00 for a couple hours on one afternoon).
My experience has been that the craps table always opens later than the full casino does, so you might want to ask a casino supervisor what time it will open on a particular day.
I had the same question before I ever sailed on Carnival and found that every Carnival ship had a craps table. I don't know why it's not usually listed in any of the brochures. I'll also say that in my experience the craps dealers are not that sharp. I've had to correct them on the proper payouts several times.
Web search engines will bring up numerous web sites on precision crap shooting. They are much better at explaining the details and how to do it than I am. I learned how and now I am one. You can be too. But the real money on a cruise ship is in roulette. Once again there is a way to gain an advantage but you have to look on the web for the info.