New York has many islands, among them Staten Island and Manhattan. So, taking a ferry in New York to get around is often a popular choice.
Among the ferries and water taxis are the Staten Island Ferry, NY Waterway, Circle Line, New York Water Taxi, and Sea Streak. Some of these are strictly for commuting and some are specifically for sightseeing, but really, when you’re on a ferry out in the water with the city’s skyline all around you, there’s always an aspect of sightseeing no matter which ferry or water taxi you’re on.
You can also take a ferry out to the Statue of Liberty, which is the main fee for seeing the monument. Most ferries and water taxis operate until around midnight, which means if you’re staying off of Manhattan, you can have fun in the city and commute back fairly late in the night with a ferry in New York.