You will need a passport when you are taking the cruise outside of the US. The reason why is so you are in different ports that you are outside of the US.
maybe yes
On most cruises yes. But not on "Closed Loop cruises" see http://getyouhome.gov for all the passport rules!
cruises to the Caribbean and Mexico can be taken with a birth certificate and a picture ID
Yes, a passport is typically required to travel outside of the country.
Yes, a passport is required to travel outside the United States.
You need a passport to travel anywhere outside your country.
No. If you're a US citizen, cruises that depart and return to the same port require only a government-issued ID and a birth certificate.
Yes, to fly anywhere that is outside of the country you live in you need a passport
You need a passport to travel internationally to any country outside of your own.
You need a passport if you are going to travel outside of the country.
As long as your are travelling outside of the Unoted States boarder, then you do need a passport.
Only if you start or end in a foreign port. Cruises are considered closed circuit journeys and as long as you begin and end in the United States you do not need a passport.