Alexandria along with destroyers , and . Hit in both of her engine rooms Bonaventure quickly sank within five or six minutes in the position with 139 casualties and 310 survivors. After observing the success of her attack, Ambra moved away. While Hereward was rescuing the survivors, Stuart, who was missed by the third torpedo, detected Ambra with ASDIC and commenced a series of depth charge attacks against the submarine. Hereward soon joined in, and attacks lasted for several hours until approximately 6:30. The submarine suffered damage to a variety of her equipment, including both gyroscopic and magnetic compasses. Once the escorts moved away, Ambra surfaced and using Celestial Navigation made her way back to Augusta. Captain Arillo received the Silver Medal of Military Valor for his performance during this patrol. On May 1, 1941, she sailed from Augusta to patrol an area outside of Alexandria. On May 5, 1941, due to a leak in one of the torpedo tubes, Commander Arillo decided to abort the mission. On May 7 Ambra returned to the base. Arillo was criticized by his superiors because they believed the failure was not severe enough to justify an early return. During May 12–20, 1941, she patrolled southeast of Malta. On September 23–24, 1941, she performed an anti-submarine patrol in the Strait of Messina together with . On October 3, 1941, she left from Augusta to patrol off Cape Zebib on the news of the suspected British moves towards the Strait of Sicily. On October 4, 1941, Ambra was called back to the base since the British threat never materialized. On the way back to Messina one of her engines failed. SLC Conversion Following the request of Captain Junio Valerio Borghese, new commander of Decima Flottiglia MAS, Ambra was transferred to that division to be converted to a SLC(Siluro a Lunga Corsa which means long running torpedo) submarine in addition to already operating . Captain Arillo was retained as Ambras commander. During the conversion, three SLC units were fitted onto the boat on her deck, two placed side by side in the aft, and one on her bow, the submarine's deck gun was also removed to accommodate SLC units and the tower was modified to better adapt for the new role. With a weight of 2.8 tons, these SLC cylinders were able to withstand depths up to 90 meters. During April 11–19, 1942, Ambra performed a