The fish, which swim many miles upstream to reach their spawning grounds, may do something that's pretty impressive for a fish. And they do often have to swim against rapids and leap to higher levels when the river is uneven.
But this dude climbed Niagara Falls:
He's the small red dot in the upper left third of the picture, on the side of the falls that freezes in the winter. The non-frozen part is doing its regular thundering down bit next to him.