For extraordinary heroism while serving on board the USS Remlik, on the morning of 17 December 1917, when the Remlik encountered a heavy gale. During this gale, there was a heavy sea running. The depth charge box on the taffrail aft, containing a Sperry depth charge, was washed overboard, the depth charge itself falling inboard and remaining on deck. MacKenzie, on his own initiative, went aft and sat down on the depth charge, as it was impracticable to carry it to safety until the ship was headed up into the sea. In acting as he did, MacKenzie exposed his life and prevented a serious accident to the ship and probable loss of the ship and the entire crew.