Up until quite recently most cruise ships and ocean liners were equipped with chapels, even if modestly sized, for the religious needs of passengers. On larger ships priests and other kinds of ministers were retained for every voyage. Indeed, one Jesuit teacher the Rad Trad had in high school made his annual vacation a cruise on Princess Line's dime in exchange for a Mass a day.
Although oceanic chapels have never been large, they were once better decorated and often explicitly denominational. The RMS Queen Mary, now a floating hotel in Long Beach, CA, had no less than three chapels, two consecrated Catholic houses and one a Jewish synagogue. The first class chapel was very nice, ornamented with a large Mother and Child mosaic and a full altar topped with the "big six." The chasuble seems to be of decent quality, too.
The book from which these pictures are taken recounts:
"I rather feared that the innovation of giving the Madonna and Child a sea-faring interest might not be approved," said artist Kenneth Shoesmith, "but as it happened, they were delighted." The panel was covered with a mosaic of gold leaf to withstand the rigors of sea air, but the greatest challenge was keeping the details correct. Father Hurley, the port chaplain at Southampton, gave ecclesiastical approval, but Shoesmith probably cared more about the sextant at the feet of the Madonna of the Atlatnic than the Papal keys in her halo.
Here we see the second and third class Catholic chapel:
The second and third class chapel, stark by contrast to the first class temple, was still well appointed. A very small image topped the altar: a medieval English styled depiction of the Crucifixion. Judging by the arrangement of the vessels and book on the altar in this picture, one wonders if this room was not also used for Anglican/Episcopalian services.
The Jewish synagogue.
These chapels were built with the demography of passengers in mind. The first class chapel was likely built for French passengers and wealthy Americans whereas the second and third class chapel probably accommodated Catholic American tourists and Catholic Europeans heading to the United States. Similarly, the synagogue was most likely built for migrant Jews trying to leave Europe.
The RMS Queen Mary 2, on which I plan to travel one day, differs from its namesake in that it does not have any chapel or religious services available.
Note: quotation and pictures taken from Images of America: RMS Queen Mary by Suzanne Tarbell, Frank Cooper, Athene Mihalakis, Don Lynch, John Thomas, and the Queen Mary Archives.