If you visit New York, you have to take one of the cruise tours. There are half island and full island tours. The tours leave every one or two hours. If you want an even more thrilling experience, take one of the night tours. Another -- more expensive -- way to visit the island of Manhattan is on a helicopter tour. It is something I regret not having done. Next time maybe.
Not far from here is the Intrepid Sea-Air-Space Museum, where you can visit the carrier Intrepid, the missile submarine Growler, and the Vietnam-era destroyer Edson.