An elongated optical fiber is vertically positioned within seawater in a deep-depth targeted zone by vertical suspension thereof from a floating buoy. Electrode sensor arrays are positioned in vertically spaced relation to each other on the optical fiber for generating warning signals in response to detection of hostile conditions. The warning signals are converted into signal data collected and transferred to a transmitter in the floating buoy from which the sensor arrays are suspended within the targeted zone positioned on the optical fiber. Such collected data signals are transmitted through an antenna within the floating buoy to locations above the seawater surface for surveillance purposes.