Is this a 596c model, 596c HD model or a 596c HD DI model?
Is the transducer mounted on the transom, inside-the-hull or on the trolling motor?
Assuming that it is the 596c or 596c HD model: set the Beam Select menu to the 200/83kHz menu setting and the SwitchFire menu to the Max Mode setting. This will be the best option for showing fish as arches.