For some time I watched as he struggled determinedly with the same rock. He would pick it up awkwardly, grunting with the weight of it as he lifted it above his tiny shoulder. Then with all his might he would throw it and watch it land right in front of him, barely touching the edge of the water. Apparently unsatisfied he would then place all of his effort into reaching for the same rock and doing it all again.
I kept watching as he repeated this several times, until he instead reached for a smaller rock and with great effort hurled it into the sea, causing a deep sounding splash. "Yes!" he cried, obviously pleased with the result of his effort.
The lesson: don't waste all your efforts on fruitless ideas. Sometimes it's the little things that make the biggest splash.