The key is to keep trying. The truth is that most cruise lines use foreigners for security (Gurkhas) but you may get a break.
One thing that helps is to actually go on a cruise and talk to someone who is in the job position you want. Find out how they got the job, and and other such details.
You might just be barking up the wrong trees. No one is going to bother to tell you they don't make the hiring decisions for the job you want.