Cruising New York - East River
The East River flows both north and south from the southern tip of Manhattan Island along the east side of Manhattan for much of its length, then turns East and eventually connects to Long Island Sound. The waterway that flows along the northern part of Manhattan Island and connects the East River to the Hudson River is known as the Harlem River. NOAA Charts 12342, "Harlem River", 12339 "East River", and 12335 "Hudson and East Rivers" are all required to cover the area.
The water in the Harlem and East Rivers contains some freshwater from minor streams and rivers, but the vast majority is seawater from two sources: the Atlantic Ocean at the mouth of New York Harbor and Long Island Sound at the eastern end of the East River. The ebb and flow of tides from these two sources cause the current in these two rivers to flow alternately in each direction - regularly at speeds of up to about 5 knots in some spots, especially Hell Gate.
The Harlem River connects to the east bank of the Hudson River at the northern tip of Manhattan Island (40°52'42" N) at a spot known as Spuyten Duyvil, from the Dutch for "Spitting Devil". The entrance to the Harlem River is spanned by a railroad bridge that must be opened to pass. It is manned 24 hours and opens by request, or is often found open if no trains are expected. Several other bridges cross the short Harlem River but have a minimum 24 ft. vertical clearance when closed and more open. These are rarely opened. Fixed bridges have clearance of at least 100 feet. There are few navigation aids but the river is deep, clear and visually navigable with care at bridges. Speed restrictions exist in some areas. The Harlem River is about 6.5 NM long ending at 40°47' N, where it joins the East River.
The East River is joined by the Harlem River at "Hell Gate", where it turns east toward Long Island Sound. Hell Gate is renowned for the strongest currents on the river at times of tidal change. The river provides passage between Long Island Sound and either the Hudson River northward via the Harlem River, or New York Harbor and the Atlantic Ocean via the East River sourthern portion.
The East River travels east about 7.5 NM from Hell Gate to Long Island Sound. It passes under the Triborough, Bronx-Whitestone and Throggs Neck Bridges. It also passes New York's LaGuardia Airport. The river handles commercial shipping and is well marked. The Throggs Neck Bridge marks the beginning of Long Island Sound.
The East River also runs north and south from Hell Gate along the east side of Manhattan. A long thin island, Roosevelt Island, sits in the middle of the East River and can be passed on either side, although the preferred passage is closer to Manhattan Island. A number of historic bridges are seen on the East River. The Queensboro or 59th St Bridge passes over Roosevelt Island. A cable tramway alongside that bridge carries passengers from Manhattan to Roosevelt Island. This section of Manhattan is the upper East Side. The United Nations building can be seen close to the river, just below Roosevelt Island. On the eastern shore of the river is the New York City Borough of Queens.
Further South, approaching the Financial District, are three more bridges, known locally as the BMW - Brooklyn, Manhattan and Williamsburg Bridges. These all cross into Brooklyn. Just south of these three bridges, on the Manhattan side is South Street Seaport, a development of waterfront food, ships and other attractions.
Governor's Island sits in New York Harbor's Upper Bay in front of the entrance to the East River and can be passed on either side.