This yellow submarine is used as a target for torpedo testing by the US Navy and its contractors. It is unmanned and towed into place when needed.
At the same dock is the US Navy’s only operational diesel-electric, deep-diving, research and development submarine, the USS Dolphin.
Employed by both civilian and Navy activities, Dolphin is equipped with an extensive instrumentation suite that supports missions such as acoustic deep-water and littoral research, near-bottom and ocean surveys, weapons launches, sensor trials, and engineering evaluations. [wikipedia link]
Contributed by Kevin.