Hey, check it out: "take a long walk off a short pier": why is the walk long and the pier short? Because the idea is that the walk will be a straight one, and will exceed in length the length of the pier, so the foolish ambulator will fall into the water! But isn't all the work here really being done by that least appreciated of speech elements, the preposition? Consider: "take a long walk on a short pier". Here, our hypothetical walking person could simply walk back and forth on the short pier several times, without once being in danger of falling into the sea, lake, or what body of water have you. Even "take a short walk off a long pier" would work, if the goal is to get the instructed party wet (provided that either a pier is within walking distance, or h/s has transportation to the pier, and that either length of a long walk is greater than the length of a long pier, or someone takes h/h part of the way down the pier).
So why not just say "walk off a pier"? The really crazy thing is that if you started at the beginning of a short pier, you couldn't take a long walk off of it—precisely because you'd be walking off of it, onto water. You can't do it! This instruction specifically sets impossible conditions for its own satisfaction. What could possibly be the point of phrasing it this way?
I hope that this will have been but the first of a series of posts in which I analyze the foolish inefficiencies of your English.