…surely, it would be an Australian Cattle Dog.
MSNBC has an article about an ACD who fell off a sail boat, swam over 5 miles to an island, then survived for 4 months on its own before being captured and re-united with its owners. The dog went wild to survive, they called her vicious and ferocious; then quickly re-adapted to her middle class life after being rescued.
Maybe it is only because I have one, but I am not surprised that an ACD is capable is of this. Any other breed and I would be surprised by the story.