刻舟求剑[kè zhōu qiú jiàn]:mark/boat/find/sword to mark the boat in order to find the lost sword.
乘船chéng chuán:take a ship/boat
渡江dù jiāng:cross a river
佩剑pèi jiàn:a double-edged sword;walking sword
记号jì hào:mark;sign signal;symbol
This idiom satirizes those who instead of taking changed circumstances account