"Linienschiffsleutnant" Hugo von Falkhausen, "U-6"s commander since November 1915, attempted to pass underneath two drifters that formed a part of the Otranto Barrage.While submerged, von Falkhausen heard an unexplained noise on the hull of the boat, which was likely the sound of "U-6" fouling one of the anti-submarine nets deployed from the drifter "Calistoga".