Black River
The Black River is the upper section of the Lamington River, which is a tributary of the North Branch of the Raritan River. On a map, it looks navigable between Ironia Road and Pleasant Hill Road. It might be early in the spring. But when we tried during the summer, we got stuck in vegetation. We tried from both ends, but made no progress.
Black River #1: Ironia Road
One launches beside a bridge, then goes south through a small overgrown pond. Beyond the pond, it is all swam. There is no river.
Black River #2: Pleasant Hill Road
One launches beside the bridge, then squeezes under the bridge and heads north. After a short while, the river turns into an impassible swamp.