As we get questions, we will answer them here.
For Carnival frequently asked questions go to: https://www.carnival.com/help
Do I need a passport to go to Cozumel?
US citizens on "closed-loop" cruises (that begin and end at the same US port) will still be able to use just a birth certificate and government-issued photo ID.
Suggestion: Apply for a passcard. They are more affordable.