One very important thing: It does NOT matter if you are or are not getting off at various islands. You need proper ID (a passport or a birth certificate and photo ID) to get ON the ship at the start and to get off the ship upon return to the USA. When you return to the USA, immigration and customs know the ship visited foreign ports. They do not know whether you got off the ship in any of those ports, and they don't care. Also, they have no particular reason to trust you. Yes, you are an honest upstanding citizen. I know that, you know that, but the feds don't know that. Also, we don't want them to just trust our word. If they did, they would also be trusting the guy who is arriving at a US immigration point who is a foreign terrorist, but is lying and saying: "No, it's cool, I'm from the US and I did not get off the ship." It is your return into the USA that really requires the proof of citizenship. Because you need to prove citizenship upon return to the USA,
DCL insists you prove it before you board. Can you imagine the hassle for DCL if they have to deal with someone who has to leave the ship but is not allowed back into the USA? Yikes! Please note, I am not trying to be mean to anyone with this post. I am not writing it in an angry nor sarcastic tone. I just noticed that a couple people in this thread mention "I'm not getting of the ship," and I think we should all understand that not getting off the ship does not really factor into the required documentation.