One of the various American flatfish; summer flounder.
(SS390: dp. 1,525 (surf.), 2,391 (subm.); l. 3116; b. 273; dr. 153; s. 20 k. (surf.), 9 k. (subm.); cpl. 66; a. 1 5, 1 40mm., 10 21 tt.; cl. Balao).
Plaice (SS390) was laid down by the Portsmouth Navy Yard, Portsmouth, N.H. 14 July 1943; launched 15 November 1943; sponsored by Miss Eleanor Fazzi; and commissioned 12 February 1944, Lt. Comdr. Clyde B. Stevens in command.
Following shakedown and training, Plaice got underway for the Panama Canal Zone 15 April, and arrived Pearl Harbor 13 May. She departed on her first war patrol in the Bonin Islands area 3 June. Plaice torpedoed and sank 986-ton ex-gunboat Hyakufuku Maru 30 June; 857-ton ex-net tender Kogi Maru 5 July; and 300-ton Submarine Chaser No. 50 on 18 July, before returning to Midway Island.
The submarine was off on her second war patrol 17 August, this time in the Nansei Shoto area. In the early afternoon 7 September, Plaice scored one torpedo hit on a Kongo Maru class liner converted to an auxiliary cruiser. On 24 September, Plaice fired four torpedoes at a Fuso class battleship, briefly stopping its screws. Three days later she sank 800-ton Coast Defense Vessel No. 10., and put three torpedoes into the side of a transport, which blossomed a bright orange flame. The patrol ended as Plaice drew into Midway 7 October and got underway the following day for Pearl Harbor with Thresher.
Plaice departed Pearl Harbor 9 November for her third patrol in the Southwestern Japanese Empire off the coast of Shikoku and Kyushu. She patrolled the traffic lanes east of Van Diemen Strait and pulled into Guam 20 December without having sunk any ships on the patrol.
The undersea raider departed Guam on her fourth patrol in the Luzon Straits-Formosa areas. Plaice was part of a coordinated attack group which included the submarine Archer Fish, Batfish, Blackfish, Scabbardfish, and Sea Poacher. This long patrol in the face of enemy antisubmarine measures resulted in but one contact worthy of torpedo fire, a convoy of a small freighter, a medium freighter and three escorts. Three attacks resulted in but one hit. On 23 March 1945, Plaice moored at Midway.
The fifth patrol originated from Midway Island 26 April and took Plaice to the Kurile Islands-Okhotsk Sea area. The first enemy contact was made 13 May, when the submarine trailed four sea trucks and four small luggers until she opened a, surface engagement with her 5-inch and 40 mm guns, sinking all four sea trucks and two luggers. When all her larger ammunition had been expended, she drove the remaining two luggers toward the beach and damaged them by 20 mm. and small arms fire. On 18 May seven fishing boats, averaging 250-tons each, hove into view. The staccato of 20 mm. and .50 caliber guns tore into two of the boats and damaged them visibly. Plaice ended her patrol at Pearl Harbor 13 June.
The sixth patrol, commencing 18 July took Plaice to the East China Sea area, but she made no enemy contacts. She picked up five survivors from an Army B25, and transferred them to a Navy patrol bomber the following day. On 15 August Japan accepted the Potsdam Ultimatum and nine days later Plaice pulled into Midway.
After the war was over, Plaice operated in the Pacific until, by directive dated November 1947, she was placed out of commission, in reserve, at Mare Island, Calif. Plaice was reactived 18 May 1963 in preparation for transfer to Brazil, 7 September 1963 under the Military Assistance Program.
Plaice received six battle stars for World War II service.