How do you translate 刻舟求劍 (각주구검)?

There is an old Chinese saying that literally translates as follows: "Notch (刻) the boat (舟) to find (求) the sword (劍). It is used to suggest foolishness.

楚(초)人(인)有(유) 涉(섭)江(강)者(자) 其(기)劍(검)自(자)舟(주)中(중)墜(추)于(우)水(수). 遽(거)契(계)其(기)舟(주) 曰(왈)是(시)吾(오)(劍(검)之(지)所(소)從(종)墜(추). 舟(주)止(지) 從(종)其(기)所(소)契(계)者(자)入(입)水(수)求(구)之(지). 舟(주)已(이)行(행)矣(의) 而(이)劍(검)不(불)行(행). 求(구)劍(검)若(약)此(차) 不(불)亦(역)惑(혹)乎(호).

There was a man from the state of Cho who was crossing a river . His sword fell out of the boat into the water. He quickly made a mark on the boat and said, "This is where my sword fell." When the boat stopped moving, he went into the water to look for his sword at the place where he notched the boat. The boat had moved, but the sword had not. Is this not a foolish way to look for a sword?