http://www.bahamas-travel.org/bahamas-cruise-passport-needed/
if I go to the Bahamas on a cruise Do I need a passport?
As the other answer said, you do not need a passport if traveling this year. That said, not a bad idea to get if possible. Passport laws have been moved back several times, they change what is going to do (you just change the rules for children and passports a day or two ago) So, the rules of the passport is very safe at this time. The government can change the rule at any time, so you may have a case. Also, if you would have to fly home for some reason (for example, a family emergency) that is necessary have a passport. All air transport needs a passport, but at this point, do not need to cruise. Have a great time!
My Disney Cruise with Mary-Kate and Ashley! 1998