Abstract: A side-scanning sonar towfish constructed from a solid polyvinyl chloride (PVC) rod is provided. The PVC rod is milled and slotted to provide recesses for electronics and transducers and slotted to provide attachment points for fins and tow rail. The entire fish is then filled and sealed with urethane thereby providing sealed solid unit. A special multi-layer acoustic matching system is bonded over the transducers to provide maximum coupling efficiency of the acoustic signal thereby allowing operation of the fish at reduced power requirements.