I know you are probably right, but this story is too haunting to not mull it over.

Obviously, the dog managed to survive some degree of hypothermia. I imagine that the length of the fur might have been a factor: the dog was not weighed down, and the fur was not so dense (long) as to not be able to dry out fairly fast.

I think that prolonged immersion in water would have killed the dog. The boat must have been fairly close to the island when it went down. A search of the island might, at least, locate Clark's body.