There's a lab cross kelpie at our local oval. Very wiggly, very fast, labrardor shaped head, kelpie tail - much fluffier all over than this one.
I'm thinking Labrador (head shape) cross greyhound (some of the tail and body shape and coat) cross a bunch of other things.
You could send off for a dna test. They're somewhere around the $75 to $150 mark - probably come back "Significant Chiuaua" (again the fur and tail)