A man from the state from Chu was crossing a river. In the boat, his sword fell into the water by his carelessness. Immediately he made a mark on the boat.
"This is wher my sword fell off", he said.
When the boat stopped moving, he went into the water to look for his sword at the place wher he had marked the boat.
The boat had moved but the sword had not. Is this not a very foolish way to look for a sword?
from L_shi chunqiu