When fishing smallmouth bass in current, use lighter line. Bigger, heavier line creates more drag in the water. The current can more easily catch heavier, thicker line than lighter line. When targeting bass stacking up in eddies behind rocks, the current might bow the line, pulling the bait away from the sweet spot. With light line, the current pushes a bait into the eddy. Many people use 4- to 8-pound fluorocarbon for targeting smallies in fast water.