Friends, one an optimist and the other a pessimist could never quite agree on any topic of discussion.  

One day the optimist decided he had found a good way to pull his friend out of his continually pessimistic way of thinking - the optimist bought a huntin' dog that could walk on water.

His plan?  Take the pessimist and the dog out duck hunting in a boat.

They got out into the middle of the lake, and the optimist shot down a duck.  The dog immediately walked out across the water, retrieved the duck, and walked back to the boat.

The optimist looked at his pessimistic friend and said, "What do you think about that?"

The pessimist replied, "That dog can't swim, can he?