http://www.bahamas-travel.org/bahamas-cruise-passport-requirement/
Cruise to Bahamas… what are passport requirements?
A friend showed me some text that said that it was still legal to use only a certified birth certificate, social security card, and state ID. But my mother and a friend’s mother saw, while on vacation in Bahamas, that a passport was required to board the ship again FROM the Bahamas.
Also, would there be an issue REentering the states without a passport?
sally b is correct for loop cruises.. but some cruise lines insist on a passport. Check with your specific cruiseline for thier policy.
After June 2009.. everyone will need a passport.
WPS/CPT Super Cruise 2011