Asama Maru
"Grayback"s tenth patrol, her most successful in terms of tonnage sunk, was also her last. She sailed from Pearl Harbor on 28 January 1944 for the East China Sea. On 24 February, "Grayback" radioed that she had sunk two cargo ships on 19 February and had damaged two others ("Taikei Maru" and "Toshin Maru" sunk). On 25 February, she transmitted her second and final report. That morning, she had sunk tanker "Nanho Maru" and severely damaged "Asama Maru". With only two torpedoes remaining, she was ordered home from patrol. Due to reach Midway on 7 March, "Grayback" did not arrive. On 30 March, ComSubPac listed her as missing and presumed lost with all hands.