The Flushing River, also known as Flushing Creek, is a waterway that flows northward through the borough of Queens in New York City, mostly within Flushing Meadows–Corona Park, emptying into the Flushing Bay and the East River.
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.
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.
The island of Manhattan is surrounded by three rivers, the Hudson River, once called North River West (to the west), the East River (to the east) and the Harlem River to the north-east.
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 short answer is “Yes!” The long answer is that it depends on when and where. Issues like sewage outflow and algal blooms keep many areas along the Hudson from being swimmable, particularly after rainfall.
It is not safe for swimming, fishing or boating especially in rainstorms. The Harlem River, a 9.3 mile long natural straight, connects the Hudson and East Rivers in New York City.