It's narrow streets are teeming with life. Especially during lunch hour, when traffic is likely at a standstill, you're are best off taking to the streets afoot. As for night-life, Nassau is famous for its countless luxury hotels, nightclubs and casinos.
New Providence is more than just fun and games, however.
As with all the islands of the Bahamas, New Providence has many beautiful beaches and protected anchorages. You might take a drive to Paradise Island or a day or weekend cruise east to Rose Island, Athol Island, Green Cay or Salt Cay. You should consult your Yachtsman's Guide for specifics, but Nassau is plenty with modern marinas, shipyards, yacht chandlers, fuel, ice and supplies of all types.