 The summer of 1917 provided few opportunities for Wainwright to test her sub @-@ killing techniques . On 4 July , a member of the destroyer 's crew spotted a purported periscope and soon thereafter others claimed that a torpedo was reported to have passed the ship , 5 feet ( 1 @.@ 5 m ) astern . Wainwright depth @-@ charged the last indicated position of the undersea raider but to no avail . On the morning of 20 August , after Rowan brought up some oil with one of her depth charges , Wainwright dropped a couple of depth charges as she passed through the faint slick . A few minutes later , she joined other ships in some sporadic gunfire but failed to prove that a submarine was in the area . 
