In April 1909, Ensign Kenneth Whiting, a future naval aviation pioneer, became the commanding officer of Porpoise.

Convinced that a man could escape from a submarine through the torpedo tube, Whiting determined that he was going to try and test his theory with himself as a guinea pig.

When the outer door was opened and water rushed in, Whiting hung onto the crossbar that drew his elbows out of the tube's mouth, and then muscled his way out using his hands and arms, the entire evolution consuming 77 seconds.

In Porpoise's log that day, Whiting had simply commented: "Whiting went through the torpedo tube, boat lying in (the) water in (a) normal condition, as an experiment..." Subsequently, becoming a unit of the First Submarine Division, Asiatic Torpedo Fleet, on 9 December 1909, Porpoise continued her routine of local operations out of Cavite for the next decade.

Renamed A-6 on 17 November 1911, she patrolled the entrance to Manila Bay and convoyed vessels out of port during World War I, under the command of Lt. A.H. Bailey.