More than once he encountered a floating log in the water. As much as he enjoyed fetching sticks and balls, and hauling large tree limbs on land, a floating branch in the water was one thing he found frightening. More than once he got stuck in the water, frantically trying to get past the log that was between him and the shore.
He also had this reaction to coming down a ladder. Now, you might wonder why a dog would ever need to come down a ladder. Pluto loved to climb ladders, and also to slide down slides. He would entertain himself on our play-set if you would just stand and watch him, climbing clumsily up the ladder and galloping down the slide. There was a slide on one side of the play-set, and a fort on the other. More than once he followed the kids up the ladder to the fort, and found himself unable to jump or climb down. He would begin to shake and bark in a very frightened voice.
Our solution was to cover the ladder with a tarp long enough for Pluto to attempt to slide down it. Typically, the tarp would go through the space between the rungs of the ladder as soon as he put weight on his paws, but he could stumble down in a fairly controlled fashion this way. Once, he followed our contractor up a ladder onto the roof of the garage, and the very understanding and heroic contractor carried him down.