Hey - I know it can be tough, even at 53 I can be shy. Not a very good conversation starter but can keep one going.
There are plenty of questions you can ask, after introducing yourself; have you cruised before, what are you going to do/did you do in port, what do you think or Carnival, O2, isn't this lame? Of course there are the standard questions; where are you from, what do you like, etc. People think you are fascinating when you let them talk about themselves. Be sure to answer their questions as well. It is a conversation not an interview