I’ve worked on a cruise ship.
The main skills required are being able to sight extremely well read and busk/improvise well.
On the gig I did there were three books of songs, one red, one yellow and the other was blue. The singer was calling out page numbers and the book colour. So blue book page 60, pick up the book, turn to the page and play. There was no rehearsing, mainly because the concert room was in constant use throughout the day.
The band played three 40 minute sets for five nights.
It wasn’t for me, it was far too regimental, I didn’t enjoy it. I was asked again a couple of years ago and said no.
I took two basses with me, but only used one.