USS Porpoise, a 107-ton Plunger (later A-1) class submarine, was built at Elizabethport, New Jersey. Commissioned in September 1903, she spent about a year on experimental torpedo firing duties at Newport, Rhode Island, then went to the New York Navy Yard for over two years of repairs and modifications. Porpoise was again active from March 1907 until April 1908, serving for some of this time with the U.S. Naval Academy at Annapolis, Maryland.

Between late April and early July 1908 Porpoise was transported from New York to the Philippines on board the collier Caesar. She began commissioned service with the Asiatic Fleet in November 1908, operating as part of the defenses of the Philippine Islands and performing experimental work. Porpoise was renamed A-6 in November 1911. Following World War I employment patrolling the entrance to Manila Bay, she was inactive from December 1918 and was formally decommissioned a year later. When the Navy's hull number system was implemented in July 1920, A-6 was designated SS-7. Later used as a target, the old submarine was striken from the list of Naval vessels in January 1922.