Cobb, I'll try and give you some background on my own experiences, may give you some more insight. Don't let anything I say put you off though. It's a great gig with great perks, but it can be difficult.
First, I never did any auditions for ships. Don't think they did them when I was doing cruises. I got lucky because a keyboard player I used to work with happened to be on a P&O ship and called me to say one of the drummers was taking some leave and did I want to sub for him for 2 weeks. I jumped at it. This was in 1993. I subbed for him on several cruises over the next 2 years in the Mediterranean, Atlantic, Caribbean.
Perks were great. Might be different these days. But back then it was free hire cars to get to the docks in the UK, and sometimes free flights if I had to meet the ship in Singapore or somewhere like that. Own cabin, tv, bathroom.
Eventually P&O offered me my own resident gig on one of their new ships in 1995. I was over the moon. Especially being tax free by being out of the country for 6 months in a year.
Up to this point it was all dance trios including backing cabarets. Eventually the musical director of the 7 piece theatre showband asked me if I'd like to do that as their drummer was leaving. It was effectively a promotion to the top gig on the ship. Less work time but harder reading and a ton of it.
I actually turned it down at first, TOO scary, lol. He said "Aww, you'll be fine. Come on, have a go at it!" Well I ended up doing it as the trio gig was coming to an end and I needed to stay working.
Let me tell you, talk about baptism of fire, lol! After coming back from some leave to start in the theatre which I was incredibly nervous about, I immediately got handed about 7 or 8 pads of music all at once. Wtf! Each one was a different show, and many with click tracks. My head was spinning. What have I got myself into I thought.
I somehow got through the first show which was a night or two later. To be honest, once you get to know the shows you really start to enjoy them. In the showband, I only ever worked 2 x 1 hour shows a night plus the occasional daytime rehearsal. Whereas in the trios, I had to work a lot more, like several shifts in the day and in the evening often up to 3am. But that was fun most of the time anyway.
Possibly the hardest thing I found was random cabarets that come on the ship because you don't get a chance to learn their dots in advance. I'd be in rehearsal with 6 other musicians who were all very experienced, everyone is handed their charts, and they're pretty much counted off as soon as the music touches the stand. So yeah, it totally sharpens your sight reading. Sink or swim really.
Continued the theatre gig for 2 years and then left ships in 99. Awesome experience in every way. I'm a decent reader but personally I always found that theatre gig a bit too hard and stressful. I did ok at it but kind of sucked in comparison to some of the other drummers I'd seen do that gig. Glad I did it though. If you get a chance to do it, 100% go for it!