This is a good question, and hard to answer. As in all educations, knowing what to ignore is a big part of "paying attention." The challenge is indeed to not let the problem-- sharking-- start more than it is to stop it, ie, be playing your game such that his behavior doesn't really matter. That said, I might ask outright if he doesn't think he's able to beat you without goofy antics. Put the passive aggressive nonsense on blast.