In late 1914, "Ocean" participated in an attack on Basra before being transferred to Egypt to defend the Suez Canal. In February 1915, she was reassigned to the Dardanelles Campaign, and she took part in several attacks on the Ottoman fortifications defending the Dardanelles. On 18 March, she attempted to retrieve the battleship after the latter had been badly damaged by a mine in Erenköy Bay, but had to abandon her salvage efforts due to heavy Turkish gunfire. She instead evacuated the surviving crew of "Irresistible" but struck a mine while making for the open sea. Badly damaged, her crew and the survivors of "Irresistible" were taken off by destroyers and "Ocean" left to sink in Morto Bay.