Images of underwater features, animate and inanimate, are produced from substantial distances in any direction around a boat, using small and easily mountable sonar devices, including three sonar transducers, two being stationary and the third being directable, the transducers being operable at various ultrasonic frequencies. Under keyboard control and using completely integrated electronic circuitry, images and echo sounding reports are generated on a graphic video display. The images include a sector-shaped image from a sector scan which covers a selected range of azimuth angles at a selected down angle.