 On 24 August 1975 their frogmen planted a mine on the river's bed below the hull of a navy destroyer, the ARA "Santísima Trinidad", as she remained docked at Rio Santiago before her commissioning.The explosion caused considerable damage to the ship's computer and electronic equipment.On 14 December 1975, using the same techniques, Montoneros frogmen placed explosives on the yacht "Itati" in an attempt to kill the Commander-in-Chief of the Argentine navy, Admiral Emilio Massera.