A system for use with a boat to provide underwater sonar images includes a GPS receiver for providing GPS position data, a left side scan sonar transducer for transmitting left side scan sonar pulses and for receiving left side scan sonar return signals, and a right side scan sonar transducer for transmitting right side scan sonar pulses and for receiving right side scan sonar return signals. The system further includes signal processing circuitry for processing the left and right side scan sonar return signals to produce side scan image data and a digital processor for causing a display to display an underwater image based upon the side scan image data, wherein the digital processor associates GPS position and side scan image data.