(SS-39: dp. 392 (surf.), 521 (subm.); l. 153'7"; b. 16'8"; dr. 13'1"; s. 14 k. (surf.), 10.5 k. (subm.); cpl. 28; a. 4 18" tt.; cl. K-8)
K-8 (SS-39) was launched 11 July 1914, by the Union Iron Works, San Francisco, Calif., under subcontract from Electric Boat Co., Groton, Conn.; sponsored by Mrs. John W. Lewis, wife of the first commanding officer; and commissioned 1 December at Mare Island, Lt. John W. Lewis in command.
K-8 departed San Francisco 26 December with K-7 for training operations along the coast of southern California. Returning to Mare Island 4 June 1915, she sailed 3 October for duty in the Hawaiian Islands, arriving Pearl Harbor 14 October. For more than 2 years she operated with K-3, K-4, and K-7, developing and perfecting submarine techniques in diving, torpedo firing, and underwater tactics. Ordered to return to West Coast 31 October 1917, she arrived San Pedro 12 November and proceeded 27 November for patrol duty out of Key West.
Arriving Key West 8 January 1918, she conducted patrols from Key West to Galveston, Tex., during the remaining months of World War I. Departing Galveston 21 November, she returned to Key West to continue experimental operations along the Florida coast until she sailed for Philadelphia 14 April 1919. Arriving 21 April, K-8 underwent overhaul before sailing 10 November for Key West. Upon arrival 3 December she began 7 months of operations in the Caribbean. After returning to Philadelphia 8 June 1920, she proceeded to Annapolis, Md., 19 January 1921, for training operations at the Naval Academy. Steaming to Hampton Roads, Va., 15 February, she continued development operations along the Atlantic coast from Norfolk to Cape Cod, returning to Annapolis 4 through 14 April and visiting West Point 24 through 30 May. She conducted experimental maneuvers in the Chesapeake Bay from 4 December to 16 May 1922; trained students out of New London, Conn., from 20 May to 5 September; and returned Hampton Roads 7 September to resume operations in the lower Chesapeake Bay. K-8 decommissioned at Norfolk 24 February 1923. Towed to the Philadelphia Navy Yard 2 September 1924, she was sold for scrapping 25 June 1931.