I would suggest your passport and make sure it is not within 6 months of expiring. Otherwise, depending on your ports, you could bring a photo drivers license with a certified copy of your birth certificate and if needed a certified copy of your marriage license. The passport is faster and with less hassle especially since 9/11. I have seen people turned away from boarding the ship because their documents did not have a raised seal (certified copy). This is your responsibility and you can loose the entire cost of the cruise. Talk to your T/A and make sure everything is in order !!!