Foul Rift is a stretch of Class II rapids on the Delaware River about a mile south of Belvidere, New Jersey, running from river mile 196.3 to 196.7. The rapids form where the river drops 22 feet over roughly half a mile across a limestone ledge in the riverbed. Despite the Class II rating, Foul Rift is regarded as the most dangerous rapids on the Delaware. At higher water levels, some of its narrower channels become extremely dangerous, giving this short reach of river an outsized reputation for hazard.