I had to cut this story to make the sermon shorter but it's a good story for a "water" sermon. It's from James W. Moore, Some Things Are To Good Not To Be True, Dimensions, p.105-106.
Have you heard the legend of the Fisher King? When the Fisher King was a boy, he was sent out to spend the night alone in the forest, as a test of his courage to be king. During the night, he had a vision of the Holy Grail—the cup used by our Lord at the last supper. He saw it surrounded by great flames of fire, and he immediately became excited by the prospect of the wealth and glory that would be his by possessing such a great prize. Greedily, he reached into the flames to grab it, but the flames were too hot, and he was severely wounded.
As the years went by, the Fisher King became more despondent and alone, and his wound grew deeper. One day, feeling sad and depressed and in pain, he went for a walk in the forest and came upon a court jester.
“Are you all right?” the jester asked. “Is there anything I can do for you? Anything at all?”
“Well, I am very thirsty,” the Fisher King replied. The jester took an old dilapidated cup from his bag, filled it with water from a nearby stream, and gave it to the Fisher King. As he drank, he suddenly felt his wound healing for the first time. And incredibly, the old cup he was drinking from had turned into the Holy Grail.
“What wonderful magic do you possess?” the Fisher King asked the jester. The jester just shrugged and said, “I know no magic. I only gave a drink of water to a thirsty soul.”