The 'Blackwater River' is a 3.1
mile (4.9
km) long
tidal inlet in northeastern
Massachusetts and southeastern
New Hampshire in the
United States.
The river forms in a
salt marsh in the northeastern corner of
Salisbury, Massachusetts by the convergence of the ''Little River'' and ''Dead Creek''. Heading north, the river quickly enters
Seabrook, New Hampshire and continues to flow through salt marsh until it reaches Hampton Harbor, northwest of Seabrook Beach, where it joins the
Hampton River.