Acoustic sensors, consisting of a concrete anchor and tethered instrument package floating above the anchor, are positioned approximately 915 meters/ 1000 yards apart along the line. The depth of the floating portion of the instrument varies with local bottom depth. For instruments anchored at less than 150 meters/ 492 feet depth (near shore), the floating portion of the instrument is within 5 meters/ 16 feet of the bottom. For instruments anchored at 150 meters/ 492 feet depth or greater, the instrument package is tethered approximately 150 meters/ 492 feet below the water surface.