What other symptoms your dog is showing? If he is also having loss of appetite, lethargy etc then some serious problem is suspected. Exposure to cold and swimming are normal factors which can cause shaking in dogs. Pain, skin parasites and nervous condition can also cause shaking in dogs. So, it will be good to see a vet for better advice.
A dog that shakes and appears to have chills was either left out in the cold and was exposed to temperatures that lowered body heat. IF this was not the case, a dog shaking is an indication of pain from some constant source.
My dog began shivering and panting really bad after we returned from a short walk. My wife found two sand-spurs, (briars), in his beard. One was imbedded in his lip. It was a sign of intense pain. Check your dog all over.
She might be scared, if not bring her to the vet and try to take her temp. See if she is running a fever. Mae sure she is warm