The prototype Fulton experimental craft was laid down at Isaac Rice's Electric Boat Company prior to these first A-class submarines.

Besides testing machinery, armament and tactics, the submarine torpedo boat also served as a training ship for the crews of new submersibles emerging from the builder's yards.

The following morning, Plunger charged her batteries and made a series of five short dives before returning alongside Apache to recharge.

Later that afternoon, Roosevelt boarded the Plunger and stayed aboard for almost two hours while she made another series of dives before returning to moor alongside the tug.

On 3 May 1909, Ensign Chester Nimitz, the future fleet admiral who would say he considered the submarines of the time "a cross between a Jules Verne fantasy and a humpbacked whale", assumed command of Plunger.

Reassigned to the Charleston Navy Yard, Plunger reached that port on 24 October and moored alongside the gunboat Castine, the tender for the Atlantic Submarine Flotilla.

Shortly thereafter, Castine's medical officer, Assistant Surgeon Micajah Boland, inspected Plunger and two other submarine torpedo boats.