Dogs and other mammals shake water off to prevent hypothermia.
Some smart guys at Georgia Institute of Technology did the math: Large dogs can rid themselves of 70% of the water in their fur with a four second shake-off episode.
Shaking speed varies by size. The smaller the animal the faster the shake. A mouse shakes 18 times per second.
A 65 pound dogs shakes 4.3 times in a second.
Watch the 2 minute video produced by Georgia Tech. It's poetry in motion set to Strauss' Blue Danube.
Read the science behind the wet dog shake: Wet Mammals Shake at Tuned Frequencies to Dry. Why the dog seeks you out before she shakes the water off is still unknown.