Courtesy of Corry Command Display:

The majority of these periscope pictures were taken by USS Guardfish (SSN 612) while on a covert submarine reconnaissance mission near the Soviet Coast in the Western Pacific in 1971.  Mission were carried out against the Soviet Union and Communist-bloc countries.

Their success provided information of the capabilities of the Soviet and other navies that could not be gathered by other means, including satellites.

Unlike our Fleet Ballistics Missile submarine colleagues, when they would hear a noise in the water the boomer would do a required turn away.  The fast attack submarine’s job was “let’s go investigate that noise.”