It's been a long time since I've been on the Staten Island Ferry. Back when I was dating, I was wooed by the cheap fare (it's now free) and the romantic views of the city, Ellis Island and the Statue of Liberty it afforded.
Go to the top deck to get the panoramic vistas during your hour-long round trip and feel free to drink a beer or two from the boat's concession stand. The total trip takes a bit longer than an hour, keep in mind you do have to depart and wait for the next ferry to take you back. It runs 24 hours a day, 365 days a year.