Get a passport book, not a card. You can not use the card for air travel and if something bad happens or you just miss your boat you could get stuck in the Bahamas with no way home. I did almost miss my boat one time in Grand Cayman because I fell asleep on the beach and was traveling solo with no one to wake me. Luckily, I found a MANIAC taxi cab driver that ran over sidewalks etc. to make sure I didn't miss the last tender.