At the beginning of December, the ship sailed from New York to Savannah, Georgia to assist in the attack on that city. Despite dismounting her main armament, the ship had to keep one or more pumps running continuously during the voyage to prevent her from sinking. She arrived at Savannah on 28 December, after the British had secured the city. Her 9-pounder guns were ordered removed when she was reclassified as a 20-gun armed transport on 22 December. Throughout 1779, "Vigilant" supported British operations along the coasts of Georgia and South Carolina, despite running aground several times. Lacking substantial repairs during this time, the ship's condition deteriorated until her crew refused to take her to sea from Beaufort, South Carolina on 28 February 1780 to support the planned siege of Charleston. She was then surveyed and condemned as "utterly unfit for sea" and decommissioned on 9 April. Her crew and armament were loaded aboard the transport "Margaret &amp; Martha" and taken to Charleston where they were transferred to the transport "Margery", which had been purchased and renamed to serve as "Vigilant"s replacement. "Vigilant" was burnt at Beaufort sometime later that year.