N.Y. Gen. Bus. Law § 262
The center of such river is hereby defined to be a line halfway between low-water mark on the east bank and low-water mark on the west bank of such river. Where an island intervenes, having an icehouse or icehouses thereon, the center of the river, for the purpose of this article, is hereby defined to be a line in each channel into which said river is thereby divided, halfway between low-water mark along the shore of such island bordering upon such channel and the banks of such river opposite such island. Where there are, or shall be, dykes erected along both banks of said river, or along either shore of such island and also along the bank of said river, opposite thereto, the center of said river is hereby defined to be a line halfway between said dykes. Where there is, or shall be erected, a dyke along one shore of such island, or along one bank of said river only, the center of said river is hereby defined to be a line halfway between said dyke and low-water mark along the opposite bank of said river, or along the opposite shore of such island, where an island intervenes. Nothing in this article shall be construed to deprive the public from the right to travel or drive over such ice for any or all legitimate purposes whatever.
N.Y. Gen. Bus. Law § 262