This idiom means being stubborn and not adapting to change.
Chǔguó rén zuò chuán guò jiāng pèijiàn diàojìn le shuǐ lǐ
楚国人Chǔguó rén🔊坐船zuò chuán🔊过江guò jiāng🔊，佩剑pèijiàn🔊掉进diàojìn🔊了le🔊水里shuǐ lǐ🔊。
Tā lìkè zài chuán biān kè le yí gè jìhào
他tā🔊立刻lìkè🔊在zài🔊船边chuán biān🔊刻了kè le🔊一个yí gè🔊记号jìhào🔊。
Chuán kào àn hòu tā cóng jìhào chù xiàshuǐ zhǎo jiàn
船Chuán🔊靠岸后kào àn hòu🔊，他tā🔊从cóng🔊记号处jìhào chù🔊下水xiàshuǐ🔊找剑zhǎo jiàn🔊。
Chuán yǐjīng zǒu le hěn yuǎn jiàn dāngrán zhǎo bú dào le
船Chuán🔊已经yǐjīng🔊走了zǒu le🔊很远hěn yuǎn🔊，剑jiàn🔊当然dāngrán🔊找不到了zhǎo bú dào le🔊。
English Translation:
A man from Chu was crossing the river by boat when his sword fell into the water. He immediately carved a mark on the side of the boat. After the boat docked, he entered the water from the mark to find his sword. The boat had already moved far away, so of course the sword could not be found.