BEWARE Major cruise lines do not advertise this way..There is a ship Named The Discovery that makes day trips to Freeport and you can get off and stay and come back at a later date. I have used her when using our timeshare over there.
However people that buy the packages like you were offered are pushed to buy upgrades in Hotels, etc and the cost goes way up. There is also local room tax not included about $12 ea a day. Go to Bahamas traveler Information exchange and you will find a ton of information about these types of trips. If you need help contact me.