Lost on Patrol
The precise date and details of her loss are unknown. She had been ordered to patrol the approaches to Manila until 10 September following a guerilla re-supply mission at Panay. Guerillas confirmed completion of this mission on 23 August, but the last communication with Grayling was received 19 August. Post-war analysis of Japanese records indicates that a surfaced submarine was sighted in Lingayen Gulf on 9 September and that a freighter had been attacked in that area on that date. There is no record of counter attacks. On the same date, the Japanese passenger-cargo vessel Hokuan Maru reported sighting a submarine submerged in shallow water west of Luzon and made a pass over it. The ship noted an impact with a submerged object, which may have been Grayling. In the absence of further communication, Grayling was declared lost on 30 September.