In the 1980's we had an American Staffordshire Terrier named Ben. (They are pretty much like pit bulls, but more upmarket. My sister who had originally owned him would never allow him to be called a pit bull.) Ben was the sweetest, gentlest dog imaginable, but large, muscular, and rather scary looking. He weighed 65 pounds.
We used to walk up by the ditch at Lake Murray, near Baltimore Drive. In those days, the water department hadn't yet invoked its scorched earth policy for the ditches near the lake, and they had a thriving ecology. Cat-tails grew in abundance, and little boys often searched among the reeds for frogs and crawdads.
One day, Ben thrust his great square nose among the plants along the water's edge, then suddenly jumped backwards with a yelp. A rather large crawdad, maybe 6 inches long and weighing at least 6 ounces, emerged from the water and began stalking toward Ben, one pincer thrust menacingly forward.
Ben backed up, growling.
The crawdad continued its attack, its pincer snapping toward Ben's nose.
Ben backed up some more. The crawdad advanced.
Ben quickly called a full retreat, and the crawdad strutted back to the water victorious.
How I wish I had had a camcorder.