This invention provides a system apparatus and method for ship-towed deployment of a non-linear volumetric array of hydrophones, allowing line-intersect or line-transect sampling of marine mammal populations through passive acoustic monitoring, enabling unambiguous real-time three-dimensional localization of single sounds received through a low-cost, modular, robust, stable, small, light, neutrally to slightly negatively buoyant volumetric array having low self-noise and low flow noise, that avoids putting high tension on the tow cable and that is compatible with standard hydrophones, instrumentation, cabling, and analytical software.