Even though the main essence of fishing is to catch fish, this type of activity can bring many other benefits in the form of Treasure Chests. These chests can contain dozens of helpful materials that would be much more difficult to obtain in other ways, but unfortunately, the chance of catching this reward is only 15%. Luckily, Magnet can increase this by up to 30%, and we'll tell you how to get it in Stardew Valley.