For me I enjoy hearing about other's work and what they do. Gives me a chance to find out more about the world around me. On the Grand Princess I met and spent time with a retired lawyer couple, husband and wife, both had their careers in the field. I enjoyed hearing about their work and it gave me a new perspective about that profession. They aren't all sharks, rats, and snakes. These were genuinely good folks that I enjoyed having wine and dinner with.
Another cruise there was a retired nurse that started in the year that I was born. I enjoyed hearing about nursing back in the 60's and 70's and she didn't mind talking about it.
And I enjoy talking about my work. Get me started on jet engines and I'll go on and on.
But I look out for the cues if someone doesn't want to talk about something. People are fairly clear with non-verbal ques or phrases that have a lot "inbetween the lines".
I think that if you don't want to talk about your work, a casual but friendly toned, "I don't care to talk about my work, especially when I'm on vacation," I think would be enough to get someone to move on to another topic. If they persisted in wanting to know, time to move on to someone else, that person is obviously going to be too pushy to spend time with.
And at the risk of offending people here but I'm getting older and don't care anymore, it seems to me that people from Europe, Australia, Canada and the US Midwest seem to be the most friendliest to meet on a cruise.