On 18 June, 1918, the U.S. submarine chasers assigned to the Otranto Barrage engaged in a submarine attack. From the War Diary of Base 25:
Units "F," "G," and "H" on barrage. Unit "G" (SC 97-179-338) Hunt Commander on S.C. 179, made sound contact with enemy submarine which was followed to the northward and eastward and at 1729, Latitute 40-19 North, Longitude 18-49 East, attacked with 17 depth charges of the 300 pound type set at 150 feet. A full report of this attack was made in report of Hunt No. 2. During the night of the 18th, Unit "F" working to the northward following a sound, having first challenged, which was not answered, opened fire. The second shot hit a British destroyer "6-A." No personnel was injured, but the destroyer was entirely disabled due to the fact that the shell had pierced the main steam line.
While there was no confirmed kill, a joint British-American inquiry was held, and it was concluded that it was probable that an enemy submarine was damaged or destroyed.