 For a month , she carried on conducting routine patrols . Action finally came on the morning of 18 October , when Wainwright again received orders to Helvick Head to hunt for an enemy submarine . She arrived at the designated location at about 11 : 15 and searched for more than two hours for clues as to the U @-@ boat 's location . Then , at 13 : 58 , she sighted a submarine 's conning tower about 1 @,@ 500 yards ( 1 @,@ 400 m ) off her starboard bow . The enemy appeared to be maneuvering into position for a torpedo attack but submerged the moment Wainwright charged to the attack . When the destroyer reached the estimated location of the U @-@ boat , she dropped a depth charge and then a buoy to mark the spot . The warship followed that maneuver with a systematic , circular search out to a radius of 20 nautical miles ( 37 km ) . Having found nothing by 04 : 00 the following morning , she gave up and shaped a course for Queenstown . 
