Harvey if you want to change it, here's what I'm trying to do. My dog doesn't shake when she exits the water, but instead shakes after she releases the fetch object. Like 98ram said, this gets me pretty wet after a few retrieves. So every time she shakes on her on I say the word shake a few times, hoping that she'll associate the word with the action. In your case though, I wouldn't worry about it unless the dog starts dropping when she shakes, because this would be disobedience, and could lead to the breaking down of your force fetch training.
"Because a duck is just a 3 pound critter"