Despite being considered a successful design by the USN, war experience in European waters demonstrated that the boats lacked the range, speed, and endurance to conduct extended patrols in the North Atlantic.

These boats were similar in size and capability to the EB design, but they had a ventrally mounted rudder and propeller shafts, a watertight superstructure to aid in surface buoyancy, and different engines and motors.

The Navy wanted some of the boats built at a west coast shipyard, so Lake sub-contracted with the Craig Shipbuilding Company of Long Beach, California to build L-6 and L-7.

For extended surface runs, the fairwater was augmented with a temporary piping-and-canvas structure (see photo) which took considerable time to deploy and dismantle.

[8] This was the first U.S. submarine class equipped with a deck gun, in this case a 3-inch/23 caliber (76 mm) partially retractable design.

The four new Lake design L-boats later deployed to the Azores in November 1918 as Division 6 to reinforce four K-class submarines sent there in October 1917.

[14] After the war, the L-class were involved in trials of new torpedoes and hydrophone equipment on both the east and west coasts before decommissioning in 1922 and 1923.