I agree with those who suggest buying really valuable jewellery at home (unless, of course, you can afford a risk). While on vacation just buy fun and unusual pieces that make wonderful reminders of that dream cruise.
While we are on the subject of jewellery, I would like to brag about my wonderful sister-in-law who bought me the most beautiful necklace, knowing how excited I was about my rapidly approaching cruise. As the X is Celebrity's logo, she gave me a lovely broad gold chain with a crystal X pendant and matching X shaped crystal and gold earrings. What a find and what a thoughtful gift.