Suprisingly, you can actually cruise without a passport, although you must have your birth certificate. There are some cruises you can go on, like if it starts at Miami, and the cruise ends at miami, then you don't need a passport. Although if it starts at Miami, and ends at Seattle then you do. Please realize if you get stranded on the island, then your done for.
How to cruise with no passport?!
Good advice. Highly recommend a passport for quickness and ease in boarding (and disembarking). The day may come when the birth certificate will no longer work.
This is valid only for US citizens cruising from a US port and only to limited destinations. Anyone outside of the states cannot even get to the cruise port without one. If you are from outside of the states you need a passport. And even if you do not need it ... you should still have one. Just makes life easier.
Here's two of many relevant articles on the subject.
Personally, I would NEVER set foot aboard a cruise ship without my passport, regardless of the itinerary.
We been using our birth certificate (all Caribbean Trips) never an issue. Just got our passports delivered during our last cruise (4/23 -5/01) so life will be easier (or at least peace of mind)
It also helps on land to, when you're not on a cruise. Certain jobs require proof of citizenship, or a "government issued ID". Some will only accept a passport.
Seattle is an island?