Manhattan is an island

Considering the fact that Manhattan is an island, the lack of waterfront access in New York City is a common enough complaint. What I find particularly frustrating though isn't so much the restricted access to the water (who really wants to swim in the East River?), but rather the under-utilization of our waterways for passenger traffic. Apparently there used to be efficient ferry service between Manhattan and Laguardia. It's inexcusable that this was discontinued, and that a similar service doesn't exist for JFK Airport. Imagine how much more useful ferry service would be than the monorail, which requires a separate commuter rail trip out to Jamaica. Some automobile and pedestrian traffic experts ought to also study the impact of a high speed ferry that would ply the East River making stops along the eastern shore of Manhattan. I'm guessing such a service would help ease the burden on the grossly inadequate 4-5-6 line. Everyone agrees that another mass-transit option is needed on the eastern East Side. A ferry to the east of Third, Second, and First Avenues would be a lot cheaper and nearly as effective as the perpetually planned Second Avenue subway line.