Do Americans need a passport for Mexican cruises?

At the moment, US citizens are not required to have a passport to travel to Mexico and the Caribbean by sea. (They must have a passport to travel by air.)

You do, however, need a government-issued photo ID (such as a drivers license) and a certified (raised stamp) copy of your birth certificate.

At some time in the summer 2008 (per the latest ruling from Homeland Security -- this could change.... again), all US citizens will need a passport to re-enter the US by any means of travel -- sea, air and/or land.