A strange discovery by Uncle Frits

Uncle Frits stood still for a moment. A 'clong' sound was not only unexpected, it was also rather strange. Carefully he once again put the shovel in the ground. Smoothly, the leaf slipped through the sand until it came across something hard. Another attempt, a little harder now, resulted in a new 'clong'.
Aunt Coby had come out at the sight of the astonished uncle. 'Beware! You will soon be through the water pipe and then we will not have a new source of food in the garden, but a very wrong water source! '