Mouth on Long Island Sound
|Source||Caleb Smith Park (at northern end of New Mill Pond)|
|- elevation||29 ft (9 m)|
|Mouth||Nissequogue River State Park at Long Island Sound|
|- elevation||0 ft (0 m)|
|Length||8.3 mi (13 km), SN|
|Volume||42.2 cu ft (1 m3)|
The river, like all other freshwater rivers on the island, is totally derived from groundwater (not from lakes).
The river begins at Caleb Smith Park in Smithtown (where special regulation trout fishing is available) and flows to Kings Park, New York. Since much of the river is an estuary canoeists travel in both directions based on the tides.
Fish found in the river include Striped Bass, Bluefish, Summer Flounder, Winter Flounder, Porgies, Eels, Brown, Rainbow and Brook Trout, Yellow Perch, Largemouth Bass, Alweives, Herring, Shad, etc.