a chinese man loses his sword in the river

Once upon a time, there was a man from the state of Chu who needed to cross a river to conduct some business. The river sparkled with ripples, and as the boat reached the middle of the river, he accidentally dropped a valuable sword he was carrying into the water. The sword made a "plop" sound as it sank and quickly disappeared from sight. Everyone on the boat felt sorry for him and exclaimed in surprise. However, the man from Chu remained calm and composed. He took out a small knife from his pocket and carved a mark on the side of the boat where the sword had fallen. Everyone was puzzled and asked, "What are you doing? The sword has already fallen into the water; what's the point of marking the boat?" The man confidently replied, "Don't worry, I have my own way. This mark indicates where the sword fell into the water. Once the boat reaches the shore, I just need to jump in from this mark and retrieve my sword." The boat continued to move forward, and the river water flowed endlessly. The man from Chu sat on the boat, gazing at the mark, feeling assured. Finally, the boat reached the shore. The man immediately stood up, took off his outer clothes, and jumped into the river according to the mark he had carved on the boat to look for his sword. He searched for a long time in the water but found nothing. By then, the river was still flowing rapidly, and the sword had long since drifted away with the current. The man climbed back onto the shore, looking very disappointed and confused: why couldn't he find the sword at the mark? Seeing his predicament, the people around him shook their heads and sighed. An old man stepped forward and said to him, "Child, the boat moves on the river, and once the sword fell into the water, it doesn't stay still with the boat but drifts with the current. The mark you made on the boat only indicates the position of the boat when the sword fell, not the actual location of the sword. How can you find the sword this way?" The man from Chu, upon hearing the old man's words, finally realized his folly and stubbornness, feeling deeply regretful.