Yes, you can travel by sea without a passport in 2026 under a specific set of circumstances known as a "Closed-Loop Cruise." This applies to U.S. citizens who depart from and return to the same U.S. port (e.g., Miami to Miami) while visiting select destinations in the Caribbean, Bahamas, or Mexico. For these specific voyages, you can use a combination of a government-issued photo ID (like a Driver's License) and an original Birth Certificate. However, this is considered a "high-risk" way to travel. If you have a medical emergency or a family crisis that requires you to fly home from a foreign port, you cannot board a plane without a passport, potentially leaving you stranded in a foreign country for days while you wait for emergency documentation from an embassy. Additionally, some countries on the itinerary may still require a passport even if the cruise line technically allows the birth certificate. For land-based sea travel, such as a ferry between the U.S. and Canada or Mexico, you can use an Enhanced Driver's License (EDL) or a NEXUS card in place of a passport. While the closed-loop rule offers a convenient loophole, travel experts universally recommend carrying a full passport to ensure you are covered for any "worst-case" scenario at sea.