(SS70: dp. 520.6 (surf. n.), 629 (subm.) ; l 1724 ; b. 18 ¼; dr. 145; s. 14 k. (surf.), 10.5 k. (subm.); cpl. 29; a. 1 3; 4 18 tt.; cl. O1)
O9 (SS70) was laid down 15 February 1917 at Fore River Shipbuilding Co., Quincy, Mass.; launched 27 January 1918; sponsored by Mrs. Frederick J. Sherman; and commissioned 27 July 1918, Lt. Oliver M. Read, Jr. in command.
During the final months of World War I, O9 operated on coastal patrol and protected the Atlantic coast from U-boats. She departed Newport 2 November 1918 for European waters, but the termination of hostilities brought the 20-sub force back to the United States.
After the war, O9 continued in Naval service and trained submarine crews at the sub school at New London. Proceeding to Coco Solo, C.Z. in 1924, the boat was reclassified to a 2nd line sub during her year there. Returning to operate at New London, O9 reverted to a 1st line sub 6 June 1928. Sailing up to Portsmouth, N.H. in January 1930, the sub returned to New London in March; the following February, she sailed to Philadelphia, to decommission there 2.5 June 1931.
Remaining on the Naval Register, O9 was recalled to training service as U.S. involvement in World War II became more imminent. She recommissioned at Philadelphia 14 April 1941 and went to New London 31 May. O9 was to see but brief pre-war duty, however.
On 19 June, O9 departed New London with other O-boats, for tests off the Isles of Shoals. After the other 2 subs had successfully completed their tests 20 June, O9 submerged at 0738 to conduct deep submergence tests; the sub did not surface thereafter but was crushed by the pressure of the water 402 feet below. The sub went down 15 miles off Portsmouth, in the area where Squalus had been lost.
Rescue ships swung into action immediately. O6, O10, Triton, Falcon, and other ships searched for the sub, and divers went down from 1300, 21 June until 1143, 22 June. Divers went to record depths for salvage operations but could stay but a brief time at the 440 depth; salvage operations were cancelled as they were considered too risky. The boat was declared a total loss as of 20 June at latitude 425948 N, longitude 702027 W. On 22 June, Secretary of the Navy Knox conducted memorial services for the 33 officers and men lost on the boat.
The boat was struck from the Navy Register 23 October 1941 and remains in the depths off Portsmouth.