Abstract: The invention relates to underwater acoustic devices and arrays formed from such devices, and which in use are suspended in water from a buoy as other flotation equipment. An underwater device in accordance with the invention comprises an elongate tubular structure which is preferably suspended from a buoy having an aerial mounted on the buoy and connected to a radio transceiver housed within the buoy, wherein the tubular structure includes a plurality of transducer elements spaced apart along a common axis, preferably by spacer tubers wherein each of the transducer elements comprises a tube, or part of a tube, composed of a piezoelectric material, preferably polyvinylidene fluoride, and electrical terminal means contacting inner and outer curved surfaces of each tubular element.