The title is neither a joke nor an idiomatic expression. This strange video is an actual footage of salmons crossing a road.
The river overflowed and it has caused a shallow flooding on the road. Then something unusual happened, someone was able to capture a video of a salmon waddling its way across the road!
That would have been an amusing accident until they realized that other salmons are doing exactly the same thing. Salmons going back to breeding grounds and traveling to higher grounds is not exactly news. But salmons taking short-cuts? Now that is definitely news.
Salmons are known to travel upstream in rivers to return to their breeding areas after spending a couple of years in the sea. Sad to say that returning to their breeding locations is literally an uphill battle which include jumping into short waterfalls, battling the currents and ‘crossing roads’.
So why do salmons cross the road? Maybe to search for ‘clearer waters’ or go to places where no salmons have ever gone before…