Li Yan, a student of water conservancy engineering, woke up from his dream and became the humble son-in-law of the Li family, a well-known water control family in Dujiangyan, Shu County, Qin Dynasty. Kong You is full of knowledge about modern fluid mechanics, but he is looked down upon because of his low status and "weird talk". Coinciding with the untamable spring floods of the Minjiang River, the county governor wanted to restart the bloody "Hebo Marriage" sacrifice. Li Yan couldn't bear it anymore and decided to use science to break superstition. He explored the river beach at night, drew the "Minjiang River Flow Map", used a simple sand table to deduce Bernoulli's equation, and publicly exposed the uselessness and cruelty of sacrifices. It also presented the astonishing "fish mouth diversion optimization strategy" to turn the decaying river center island into a magical dam. Faced with the difficulties of the conservative witch Zhu and the incomprehension of the Yue family, he opened the "Water Conservancy Gewu Hall", using bamboo tube buoys to demonstrate the secrets of water flow, and enlighten craftsmen and people step by step. From being a son-in-law to being a "right man", Li Yan used science as his blade to cut through ignorance.
