One Day in Nassau
Since cruise ships normally arrive at Nassau fairly early, there is quite a bit you can do in a single day. It all depends on whether you want to be active and go out on your own, arrange a tour or indulge in a day at the Atlantis mega-resort on Paradise Island. (See Nassau Things To Do)
Let's start with option that so many people seem most interested:
Day (Pass) at Atlantis
If you are interested in guided tours, consider this option--and compare these with your cruise ship prices. Everyone--hotels and cruise ships--normally use the same land operators. Cruise ships usually add a 10%-20% fee.
Half-Day Self-Guided Nassau Walking Tour
Thanks to its convenient location, Nassau's cruise port is within a half-day walk of many major attractions. Personally, I would rather walk around a town as opposed to seeing it through a glass window while be driven around. By walking, you can spend as much time as you wish.
If you turn left at East Hill Street, you can visit Government House and Graycliff, Nassau's best restaurant, and its cigar factory.