We had a water feature at the bottom of our last garden. It was a series of copper leaves that the water ran over. I thought it was very restful, and GS loved it when he was little, but he was overfond of feeding pea gravel down the tube that the water came up, which wasn't helpful. He would also make a great game out of placing various sizes and shapes of pebbles on the leaves and watching the water run over them which tended to overbalance the whole thing. One day he decided to be really helpful, as he had heard DH say the sump could do with cleaning out. He got a bottle of washing up liquid and squirted it over the leaves, which produced a foam fountain of epic proportions and ruined the pump. DH wasn't entirely unhappy as he thought the whole thing was a colossal waste of space and more trouble than it was worth, but me.... .