The Greater Underwater Propulsion Power Program (GUPPY) was initiated by the United States Navy after World War II to improve the submerged speed, maneuverability, and endurance of its submarines. (The "Y" in the acronym was added for pronounceability.)
USS Greenfish after GUPPY III modernization. Visible on deck are the three distinctive shark-fin domes of the PUFFS sonar.
Pomodon after GUPPY I.
USS Cubera, after GUPPY II modernization
USS Thornback after GUPPY IIA modernization
Ship Characteristics Board
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The Ship Characteristics Board was a unit of the United States Navy.
Project SCB 1 result: the USS Norfolk (CLK-1/DL-1)
Thresher, the first result of project SCB 188, at sea on 24 July 1961