I'm not Catholic, so don't pay a lot of attention to such things but I can recall several cruises on larger ships (I can't say ALL of them) where there was a Float-A-Priest aboard who offered Mass each day.
I was on the Ocean Princess in October and they had a Mass Saturday night by a Monseigner and a priest ... never saw anything about a daily Mass. I've heard that priests can travel free but have to provide their own transportation to the ship so it has kind of depended if there were a priest on board. I was on the Splendour of the Seas (RCL) last year and there wasn't a Mass - just a non-denominational gathering on Sunday.
I'm one of them!
Leaving tomorrow for HAL's Zaandam.
I know HAL usually has a priest on board for daily Mass. I was on Celebrity's Summit after Thanksgiving for same. I know Celebrity wants to take a priest on their cruises, but clergy availability is sometimes difficult.
I'm thinking of going on another cruise in June maybe, and then again next fall.
Traditionally one does not have to Mass at all if travelling. The interesting question is that of going if offered on the "premises"..All the cruises on which I have been that had a priest aboard offered Mass every day, which makes sense since Roman Catholic priests celebrate Mass daily. JP