A former name retained.
Lydonia (SP‑700) was built by Pusey and Jones, Wilmington, Del., in 1912; acquired by the Navy 21 August 1917 from William A. Lydon; and commissioned 27 October 1917, Lt. Cmdr, R. P. McCullough in command.
After repairs and target practice off Bermuda, the converted yacht departed the Caribbean in mid‑November and arrived Horta, Azores, 7 December 1917. Two weeks later she arrived Gibraltar to join the U.S. patrol squadron operating along the Atlantic and Mediterranean sides of the Straits of Gibraltar.
Assigned the task of protecting Mediterranean supply convoys, Lydonia remained on constant vigil for deadly U‑boats during the early months of 1918. She made two attacks on enemy subs in February while guarding Allied convoys and although the results were negative, the experience was to pay off at a later date.
On 8 May, Lydonia was steaming with a convoy from Bizerte to Gibraltar when she encountered German submarine UB‑70. With the British destroyer Basilisk, the patrol craft made coordinated depth charge attacks at 1735, after the British merchant ship Ingleside was destroyed by a torpedo. After 15 minutes of running battle, the attack was curtailed and survivors of Ingleside were rescued. Heavy seas prevented an immediate assessment of possible damage to the submarine, but later evaluations credited Lydonia and Basilisk with sinking UB‑70.
For the rest of the war, Lydonia continued escort operations from Bizerte to Gibraltar, playing a major role in the free movement of vital wartime supplies. Calling in Azores and Caribbean ports en route to the United States, she arrived Hampton Roads, Va., 6 February 1919. Lydonia decommissioned at Norfolk 7 August 1919 and was transferred to the Coast and Geodetic Survey the same day.