A production method for a headline sonar cable (20, 120, 220, 320, 420) that exhibits a high breaking-strength and lighter weight than a conventional steel headline sonar cable, characterized by the steps of: a. providing a first strength member (14); b. forming an elongatable internally-located conductive structure (34, 134, 134x) about the first strength member (14), the elongatable internally-located conductive structure being adapted for data signal transmission; and c. braiding a strength-member jacket layer (52) of polymeric material around the structure (34, 134, 134x) while ensuring that the structure (34, 134) is slack when surrounded by the jacket layer (52). The structure (34, 134, 134x) of the cable conductivity upon stretching of the jacket layer (52) surrounding the structure (34, 134, 34x) that lengthens the cable. For one embodiment of the method a braided conductor (122) formed about the first strength member (14) and also enclosed within a braided sheath (132) and a layer of polymeric layer (124) forms the structure (34, 134). For another embodiment another conductor and especially an optical fibre or optical cable and associated structure is wrapped around the braided conductor (122) by being wrapped around the exterior of the layer of polymeric material (124) within which is enclosed the braided conductor formed about the first strength member (14). In other embodiments, further thermoplastic layers (124x, y and z) and further sheaths (132x, y and z) are employed in forming bundled arrangements of conductive structures for various alternative headline sonar cables.