I would also be a tad wary of buying high end gems unless you can tell a real one from a fake. There are some man-made stones now that are almost impossible to tell unless they are tested. Even a loupe isn't adequate to test them. I would talk to someone who works on the ship about the policy regarding bogus gems. I think that the "recommended shops", which are always pricier than the others will allow you to return one through the cruise line if you find out it is not what you thought.