Cruise line key cards

I have a phone app that can copy Mifare Ultralight C cards. These are used on a popular cruise line. They have no passwords set and are therefore easy to copy. I would like to copy my room key to a fob on my next cruise. Is it likely that I would need a "magic" fob to clone the UID? If I am able to copy the entire data section, is there any other security that could have been implemented that would cause it not to work?