Fishfinders are a specialized type of echo sounding system using an active sonar and relays the fish and other objects on the display.

Generally a fishfinder will rely on the availability of a transducer. Transducers are more common in the transom-mount form as they are more portable and do not require drilling holes through the hull of your boat where as thru-hull do.

Fishfinders send an electric impulse from the transmitter and converted to a sound wave via the transducer. When the sound wave hits an object the wave is bounced back to the fishfinder and the information is then transferred to a readable form for the fisherman to make a decision where to fish.

With recent enhancements in technology there has been a lot of convergence between fishfinders, chartplotters and GPS equipment.