Rivers, the largest of which is the Hudson River, which originates in the Adirondacks and flows south to New York Harbor. From the City north to the Federal Dam at Troy, NY, the Hudson River is a tidal estu- ary. Other rivers include the Bronx River and Hutchinson River.
Technically it's legal to swim in the East River, although it's also strictly forbidden to actually enter the river. Legalities aside, Mike Dulong, senior attorney for the New York water quality advocacy group Riverkeeper, claims that the East River isn't as unsanitary as the average New Yorker might assume.
The East River is a saltwater tidal estuary in New York City. The waterway, which is actually not a river despite its name, connects Upper New York Bay on its south end to Long Island Sound on its north end. It separates Long Island, with the boroughs of Brooklyn and Queens, from Manhattan Island and from the Bronx.
Manhattan may not be the biggest river island in the world, we'll come to that later, but it is the most densely populated of the five boroughs that make up New York. More than 1.6 million people squeeze into an area marginally larger than Kowloon and slightly smaller than Hong Kong Island.
The Hudson River is the defining natural feature of a major region of New York State, familiar to millions who drive across its bridges, admire its grandeur from parks and historic sites, or ride the Hudson River Line railroad.