Use "unnavigable" in a sentence

1. Antonyms for Crossable include impassable, impassible, unnegotiable, unpassable, unnavigable, blocked, closed, obstructed, superior and exceptional

2. The Madeira-Mamoré Railroad runs in a 365 kilometres (227 mi) loop around the unnavigable section to Guajará-Mirim on the Mamoré River.