Abstract: An apparatus for locating, classifying and identifying underwater marine animals by means of the sounds they make includes an elongated submersible array adapted to be towed in various directions. The array is made up of subarrays of multiple hydrophones which are arranged along the length of each subarray in groups. By changing the combinations of groups, the frequency response and the directional sensitivity of the array can be varied. The outputs of the groups can be selectively analyzed both visually and audibly for characteristic fish sounds. The received sounds are classified and used for the identification of newly found fish.