The stone that wouldn't sink

The Danube River was high that night because of the heavy rain that had fallen the previous day. The Danube carried branches and cold foam, it breathed deeply as if the Danube were a living being. I was standing on the bank with a pebble in my hand and I was choosing the right one to throw into the river and have fun. An old man was sitting a few steps away, on an overturned boat. I didn't hear when he came, he just appeared in front of me "Three times," he said. "If he skips three times, let him go." I swung. Once. Twice. The third time it sank without a sound. "Again," he said. The other stone was darker. He jumped too high and disappeared. "Not that one." We sat down. The river was doing its thing. "How do you know which one it is?" I asked. He turned the stone in his hand. "You don't know. You recognize the one that won't hurt you when you let it go." I took the third one. Ordinary. I threw it away. Once. Twice. The third time it slid across the surface and disappeared. The old man nodded. "That one." "Now what?" "You can go now." "Where?" "Where are you headed." That made me angry. "If it's that simple, why are you here?" He looked at the river. "Because I once threw a rock that wanted to sink." We were silent. The cold was climbing up the coast. "How long?" I asked. "Enough." "And before that?" "I thought I knew." Something fell into the water. The sound was dull. "Show me the path." He stood up and pointed upstream. "Follow the edge. When the river dies down, turn left." "And you?" "I'm staying." I started. The river was getting quieter. The path opened by itself. I stopped and turned around. The shore was empty. A boat without a shadow. I felt a stone in my pocket. I don't remember keeping it. It was smooth. Heavy as it should be. This time, I didn't throw it away.