Ares there –
and for all his war cries Diomedes shrank at the sight,
as a man at a loss, helpless, crossing a vast plain
halts short at a river rapids surging out to sea,
takes one look at the water roaring up in foam
and springs back with a leap. So he recoiled.

– Homer

The Iliad, Book 5, lines 684-689. Diomedes backs away from the god of war Ares on the battlefield. An epic simile compares him to a man crossing a plain forced to halt when he comes upon a raging river surging out to sea.