For travel by sea, you don't need a passport for re-entry to the United States but you do need some kind of documentation (see link below). If you are traveling by air, then yes you have to have a passport.
It depends on your country of origin.
you only need a passport if you are going to cruise to they place and fly back but it you were cruising from lets say Florida to the Bahama's and you don't stay in the Bahamas and cruise back then you don't need one
yes you do need a passport throghout the cruise, especially to get out of the Bahamas visitor center,but when you go back on the cruise they will give you a carnival card.
You do not need a passport to cruise ONLY if you are on a "closed loop" cruise from the United States. (i.e your port where you embark on is in Florida and at the end of your cruise you come back to Florida to disembark.) If you are starting or ending your cruise in another country then you will need a passport. Also check the U.S customs and borders web site. www.WHTI. Gov
Yes, you need a passport. If you are leaving the USA and going to Mexico then you need a passport.
yes you do, you also need one for Canada, the Bahamas, and Bermuda now.
If you want to enter a foreign country you do. The passport isn't for leaving the country of citizenship. Its for entry into foreign countries. Even some cruise lines require a passport. To get back into the country you also need one. All American citizens now need a passport.
You don't need a passport to go, however, if anything happens to your ship (even small damages) and they want to transfer you to another ship to get back into the US, you won't be able to do so without a passport, and you would be stuck wherever on your own dime. The cruise company wouldn't pay to get you home if you didn't have a passport, and you'd need to pay for your arrangements there, not to mention however long it takes to get back. Get the passport, better safe than sorry.
If you are a Mexican, Canadian or American citizen you can cross the border on foot or by car with a valid photo ID. As of July 2011 you still do not need a passport. If you were to arrive by air or Cruise ship you would need a passport.
Yes. Everyone entering the US by boat or air or foot must have a US Passport for reentry. This became effective in June 2009.
yes, you will be traveling to a foreign country and back to the USA
Actual passports are not required if you are leaving the country by land or boat. However, passport cards are required in order for you to enter back into the US. Passport cards are similar to drivers licenses and cost less than actual passports.
No, but you will need a passport to get back into the US.