@Laotionne - I wish I could tell you exactly what items and types of experiences cruise ships are looking for in their musicians, but I imagine it varies a little depending on the individual conducting the interviews and the number of good applicants available.
I knew a musician, a guitar player and singer, when I worked for a resort. He played in the dining room and in the bar at the resort. He was very young and didn't have much work experience. We used to joke that he only knew three songs because those were the ones he always played.
I was surprised to hear that he later landed a job on a cruise ship. I guess the cruise director really liked his three songs. Seriously, working at the resort was good experience for him because the job is similar in some ways to working on a ship. In both places, he was playing for people who were on vacation and relaxing.