Sonarbouys are buoys equipped with active or passive sonar designed to find sub-surface threats. Dropped from Anti-submarine warfare (ASW) helicopters and patrol aircraft they are set in long lines within a patrol area. Each line has a number of active and passive buoys. While the majority of sonarbys are above the thermocline layer some can be dropped below to find submarines running deep. In command the hotkey '[' drops a passive buoy and ']' drops an active bouy. Pressing shift and either key drops the buoy below the layer.