"Triumph" participated in the main attack on the Narrows forts on 18 March, and fired on Ottoman trenches at Achi Baba on 15 April. On the night of 18 April, one of her picket boats and one from "Majestic", both armed with torpedoes mounted in dropping gear, attacked the British submarine , which had stranded beneath Fort Dardanos and was being salvaged by German and Ottoman forces; a torpedo from the "Majestic" boat destroyed the submarine. "Triumph" supported the main landing by the Anzac forces at Gaba Tepe on 25 April, and continued to support them through May. On 25 May, the ship was underway off Gaba Tepe, firing on Ottoman positions, with torpedo nets out and most watertight doors shut, when she sighted a submarine periscope off her starboard beam at about 1230 hours. It belonged to the U-boat under the command of Lieutenant Otto Hersing."Triumph" opened fire on the periscope, but was almost immediately struck by a torpedo, which easily cut through her torpedo net, on her starboard side. A tremendous explosion resulted, and "Triumph" took on a list 10° to starboard. She held that list for about five minutes, then it increased to 30°. The destroyer evacuated most of her crew before she capsized ten minutes later. She remained afloat upside down for about 30 minutes, then began to sink slowly in about of water. Three officers and 75 enlisted men died in her sinking.