The two submarines of the Porpoise group were developed by the Bureau of Construction & Repair at the Portsmouth Navy Yard.

All ten submarines carried the same armament and propulsion machinery, and had the same operating characteristics and thus were considered to be the same class.

This allowed extended patrols in Japanese home waters, and would remain standard through the Tench class of 1944.

[6] Although it proved successful with improved equipment beginning with the Tambor class of 1940, the diesel-electric drive was troublesome at first.

[12] Pompano would be the sole boat of the class fitted with the Hooven-Owens-Rentschler Model 89DA, an innovative double acting diesel engine.

Unfortunately, these engines gave Pompano considerable trouble due to excessive vibration and improperly forged gearing.

[13] Five of the class received an additional pair of external bow torpedo tubes, probably early in World War II: Porpoise, Pike, Tarpon, Pickerel, and Permit.

[17] These boats were all built with a large bulky conning tower fairwater with an enclosed (but free-flooding) wheelhouse and a surface steering station at the forward end.

In October 1941 most of the front-line submarine force, including all sixteen Salmon and Sargo class boats, joined them.

The Japanese occupation of southern Indo-China and the August 1941 American-British-Dutch retaliatory oil embargo had raised international tensions, and an increased military presence in the Philippines was felt necessary.

The conning tower fairwater was reduced in size in a fashion similar to the other fleet submarines, with both the forward and after sections cut away.