"Seahorse" spent the first part of her sixth war patrol supporting the capture of the Palaus and then headed for the Luzon Strait. Despite intensive efforts, the submarine could locate only one worthwhile target, "Coast Defense Vessel No. 21", a frigate of 800 tons, which she sank. Five days later, "Seahorse" took up lifeguard station for the carrier airstrike on northern Luzon and then returned to Midway on 18 October. Upon completion of an overhaul at Mare Island Navy Yard, "Seahorse" put to sea on 9 March 1945 for her seventh war patrol. Following patrol in the Tsushima Strait, she sank a small junk with gunfire on 8 April. On 18 April, an attack by two patrol boats ("CD-14" and "CD-132") left the submarine's interior a shambles of broken glass, smashed instruments, and spilled hydraulic oil. "Seahorse" made hasty repairs and headed for Apra Harbor, Guam, and then to Pearl Harbor for overhaul. "Seahorse" put to sea for her eighth and final war patrol on 12 July. When hostilities ceased on 15 August, the submarine was on station southeast of Hachijō-jima. Following her return to Midway, "Seahorse" sailed for Mare Island where she was decommissioned on 2 March 1946. She was assigned to the Pacific Reserve Fleet and remained inactive for the remainder of her career. She was reclassified an auxiliary submarine, AGSS-304, on 6 November 1962, struck from the Navy list on 1 March 1967, and sold on 14 December 1968 to Zidell Explorations Inc., Portland, Oregon, for scrapping. "Seahorse" (SS-304) received nine battle stars for World War II service.