Long ago it had been a thing of rapids and waterfalls, ferocious and all but innavigable for hundreds of miles.

An innavigable sea washes with silent waves between us and the things we aim at and converse with.

To seal his sacred vow, by Styx he swore, The lake of liquid pitch, the dreary shore, And Phlegethon's innavigable flood, And the black regions of his brother god.

Because the river had become almost innavigable between Oxford and Burcot, goods destined for Oxford had to be unloaded from barges at Burcot and carried by wagons to Oxford.

But if so dire a love your soul invades, As twice below to view the trembling shades; If you so hard a toil will undertake, As twice to pass th' innavigable lake; Receive my counsel.

This let me crave, since near your grove the road To hell lies open, and the dark abode Which Acheron surrounds, th' innavigable flood; Conduct me thro' the regions void of light, And lead me longing to my father's sight.