Passports
Yes, you must have Passports to travel to the Bahamas from the US or anywhere else.
US citizens that need Passports can go here: http://travel.state.gov/passport/get/first/first_830.html
Canadian citizens: http://www.ppt.gc.ca/index.aspx
Health Information:
No special precautions or shots are usually necessary, but for additional information from the CDC you can go to:
wwwnc.cdc/travel/destinations/clinicians/none/the-bahamas