This recent article does a good job of explaining what the new rules mean for cruisers, but if you scroll all the way to the bottom and read the comments you’ll see that even travel professionals have a hard time interpreting all the guidelines.
Yes, there are still loopholes (like “closed loop” voyages) and less expensive options (like the “passport card“), but the safest course of action is to just go ahead and get a passport. It costs just $100 (less for children), it’s good for 10 years (5 years for kids 15 and under), and it’s the most universally accepted form of identification.
Plus, with a passport in your pocket, you’re ready for any last-minute travel opportunity that arises!