Amidst continuous torrential rain, modern water conservancy engineer Lu Chen time-travels to become a debt-ridden scholar. Using a bronze fish amulet to foresee the flood peak, he is treated as a madman by the villagers. After house foundations collapse, he leads Lu Dahe and A He to craft a raft that rises with the water level, using waste to build fire channels, fuel, and habitable floating houses, establishing a water city amidst floods, famine, power struggles, and imitators. Facing Shen Qiuniang who once severed ties with him, the Zhou family who monopolized grain boats, and out-of-control disaster victims, Lu Chen uses engineering, rules, and repeated rescues to prove that survival is not waiting for miracles, but turning every inch of buoyancy into order.