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 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 . Having found nothing by 04:00 the following morning, she gave up and shaped a course for Queenstown.