I consider myself an introvert and cruised solo for the first time last year. From my experience, it is much easier to strike up conversations on a cruise because you already have something in common with everyone around you - you are enjoying your vacation! Out in the real world if you are waiting in line for coffee in the morning, you are surrounded by people in varying stages of morning routines/rushing around, thinking about work and school drop offs and to do lists, whereas waiting for your coffee on your cruise? Everyone is just looking forward to what's ahead that day, completely different mindset. I also found that a simple compliment can either strike up a conversation or, if the recipient isn't interested in chatting, you at least feel good for providing a compliment. I often carried a book around with me and when I saw another "book person" it was a great ice breaker. Don't overthink it or worry about it, I am sure you will meet some great people and have a wonderful time!