Poor Noba, I hope he's ok. He may have what's known as "dead tail" Nebo has had this twice from swimming. It sounds like the same symptoms, if it is that, it will heal itself in a few days. Hopefully it's that instead of a break, good luck at the vet. Here's some links about it http://www.woodhavenlabs.com/coldtail.html
http://www.working-retriever.com/library/cwtail.html