 "Half Moon" was laid down as a small seaplane tender (AVP-26) on 10 March 1942 by Lake Washington Shipyards, Houghton, Washington, and was launched as such on 12 July 1942, sponsored by Mrs. T. A.Gray.In March 1943 she was selected for conversion into a motor torpedo boat tender and redesignated AGP-6, but she was so close to completion as a seaplane tender that it soon was decided to convert the seaplane tender USS "Oyster Bay" (AVP-28) into a motor torpedo boat tender instead; "Oyster Bay" was designated AGP-6 and became .