sentences:  "Opportune" was laid down 13 September 1944 by Basalt Rock Company in Napa, California; launched 31 March 1945; sponsored by Mrs. Kenneth Sanger; and commissioned at Mare Island, California, 5 October 1945, Lt. Comdr.Charles L. Knopp in command.After training on the California coast, "Opportune" sailed from San Pedro, California, 11 December 1945 for San Juan, Puerto Rico, her base for the next eight years.