navigable

The U.S. has been arguing for 53 years now over the definition of two words in the 1972 Clean Water Act: “navigable waters.”

Stretching from Alaska to the pencil tip of Argentina, the 48,000km-long Pan-American Highway holds the record for the world's longest road navigable by motor vehicle.

Ben Cottam is the director of the Canal and River Trust for Wales which looks after navigable canals and waterways.

They have sections of challenging rapids, but are usually only navigable for two or three months in early summer, according to Briancon's official website.

Some are navigable, as we saw in “Six Feet Under.”