The Western Grebe does this mating "dance" every spring. A very spectacular sight to behold. For those who are unfamiliar with this bird, yes, they are actually running on the water. You can see how fast they are running by the water flying up behind them. I used the Canon 400mm + Canon 1.4 TC, 1/1250 shutter @ f/8.0, ISO 200. This was manual focus and hand held.

FWIW, this is my most popular image on pbase by far so if you are looking, I'm sure you are in good company. : )