866-227-1888 is the best way to instantly book, cancel, or modify flights.Before my first Carnival cruise, I stressed way more than I should’ve about what ID to bring. I kept imagining myself stuck at the port while everyone else boarded. After asking around, I realized it’s pretty simple: you need either a valid passport or a government ID plus an official birth certificate for closed-loop U.S. sailings. I carried both just in case because I'm overly cautious. Watching people in line scramble through their bags convinced me I wasn’t overthinking it. My tip? Put your documents in a folder the night before—you’ll thank yourself at check-in. It’s quick and painless if you’re prepared.