[1] For surface running, the Electric Boat submarines were powered by two 450-brake-horsepower (336 kW) diesel engines, each driving one propeller shaft.

Following the United States's entry into World War I, the submarine protected Allied shipping lanes to the European countries.

Departing New London, Connecticut, on 27 November, L-3 sailed for the Azores via Bermuda arriving Ponta Delgada on 13 January 1918.

One month later, she was dispatched to the British Isles for patrol duty out of Berehaven, Bantry Bay, Ireland, to protect Allied shipping losses from U-boat attacks.

Remaining in British waters throughout the war, L-3 departed the Isle of Portland, England, on 3 January 1919 for the United States, arriving Philadelphia, Pennsylvania, on 1 February.