USS PGM - 18 USS " PGM - 18 was a built for the United States Navy during World War II . She was built and originally commissioned as USS " PC - 1255 , a , and was decommissioned and converted in late 1944 . USS PGM - 18 struck a mine off the coast of Okinawa in April 1945 ; 13 men lost their lives when " PGM - 18 " sank . Career . " PC - 1255 " was built by the Luders Marine Construction Company in Stamford , Connecticut . She was laid down on 29 September 1943 and launched on 23 January 1944 . She was commissioned as USS " PC - 1255 " on 1 September 1944 . She was decommissioned in October 1944 and converted into a gunboat at the Dade Dry Docks Shipyard in Miami , Florida . She was recommissioned as USS " PGM - 18 " on 18 December 1944 . She was destroyed on 7 April 1945 after striking a mine and foundering off the coast of Okinawa during the Battle of Okinawa . After being commissioned as USS " PC - 1255 " , the subchaser received her captain , Lieutenant John C . Bigham , Jr . , USNR . She spent the first month of duty receiving her crew , bringing on supplies , and being inspected and inventoried . On 16 September 1944 , she set sail for the Naval Training Center in Miami , Florida , arriving there on the 19th . The next day " PC - 1255 " received orders to report to the Dade Dry Docks Shipyard to undergo conversion from a submarine chaser into a patrol gunboat . Her submarine hunting technology and antisubmarine weapons were replaced with six 20mm , one twin 40mm , and one twin . 50 caliber machine guns and a 60mm mortar . She was decommissioned in October 1944 at the start of the conversion and recommissioned as USS " PGM - 18 " when the conversion was finished on 18 December 1944 . With her conversion complete , " PGM - 18 " returned to the Naval Training Center to undergo shakedown training . The training lasted for two straight weeks of intense drills and exercises , excluding Christmas Day and New Years Day . With her training complete she spent the next several days getting her hull scrubbed clean and repainted . On 17 January 1945 she set out for San Diego , California via the Panama Canal , arriving there on 2 February . " PGM - 18 " spent several days resupplying before dispatching to Pearl Harbor , Hawaii , arriving there on 14 February . While at Pearl Harbor , the ship ' s captain , Lieutenant Bigham , broke his ankle and was replaced with Lieutenant Cyril Bayley , USNR . On 26 February , she set out for Eniwetok Atoll with fellow gunboat , USS " PGM - 29 " . On 28 February 1945 , an unidentified ship approaching the pair of gunboats at an overtaking parallel course opened fire , firing two rounds which fell short . The unknown ship reversed course and attempts to contact her failed . " PGM - 18 " monitored a radio message reporting a sighting of a submarine . " PGM - 18 " proceeded to send out a message reporting that the submarine sighting was false and that they had been mistaken for a submarine . Due to the low profile of PGM gunboats and PC submarine chasers it was not uncommon for them to be misidentified as a submarine . Later , the same ship overtook them and was revealed to be US Army freighter , . On 6 March 1945 , the two gunboats arrived at Eniwetok . While anchored , " PGM - 29 " was accidentally struck by Liberty ship . While she underwent repairs , " PGM - 18 " proceeded without her to Guam and then to Ulithi . After a week of shoreleave , she proceeded to Kerama Retto , Ryukyu Islands with a group of " YMS - 1 " class minesweepers . Throughout heavy kamikaze attacks during the Battle of Okinawa , " PGM - 18 " and the minesweepers successfully cleaned up Japanese mines at Kerama Retto and off the west coast of Okinawa . The minesweepers turned their attention to the waters of Nakagusuku Bay . " PGM - 18 " , while following behind " YMS - 103 " and destroying mines she and other minesweepers cut loose , struck and detonated a mine . Eyewitnesses on nearby ships reported that the explosion was so powerful they could see five feet of sunlight under her keel before she came back down into the water , rolled over , and then foundered . " YMS - 103 " , in an attempt to rescue survivors , struck two mines , blowing off her bow and stem . Despite this , she was able to remain afloat . " PGM - 18 " suffered thirteen dead or missing and " YMS - 103 " suffered five killed and seven wounded . The survivors were picked up by other ships in the area . " PGM - 18 " was only in service for 111 days before her destruction and received a battle star for her involvement in the Battle of Okinawa .