Wi-Fi Calling lets you talk and text from indoor locations where itâs hard even for a strong cellular signal to reach. Wi-Fi Calling can be used in the Domestic Coverage Area (U.S., Puerto Rico, and U.S. Virgin Islands) and from most international countries.
The U.S. Passport Card. This... is the U.S. Passport Card! This card can be used as an official I.D. in many countries abroad. However, it cannot be used for international travel by air. If you are going to travel to an international destination, you will still need to take your passport book with you.
Again, you don't need a passport book or card to go on a closed loop cruise. All you need is your birth certificate showing you were born in the US and official photo I.D. But, in case you were interested in the passport card I've provided a link below.