just tight line it. Try holding it at different depths until you find out what depth they are. Start at the bottom and then come up a little a little at a time and see where you get bit the most. Just move around different spots and do that each place. maybe you'll find just the right spot and depth that's holding some fish. Crappie most likely be close to a pier post or some submerged structure right at or under the pier. Unless something is sunk out away from the pier.