David Swartwood was born on March 17, 1923, in Greensburgh, Pennsylvania. He enlisted in the U.S. Navy on January 12, 1942, and completed basic training at NTS Great Lakes, Illinois, in March 1942. His first assignment was aboard the submarine tender USS Fulton (AS-11) from March to April 1942, followed by service aboard the submarine USS Gato (SS-212) during her first war patrol from April to June 1942. Sea2c Swartwood then transferred to the submarine USS Grunion (SS-216), serving aboard her from June 1942 until he was killed in action during a confrontation with the armed Japanese freighter Kano Maru on July 30, 1942. On August 22, 2007, a search team organized by the three sons of CDR Mannert Abele (the Captain of the Grunion when she was sunk) used a remotely operated vehicle to find a sunken vessel 3,000 feet down in the Bering Sea north of Kiska Island at the tip of the Aleutian Islands. On October 1, 2008, the U.S. Navy announced that the sunken vessel is the World War II submarine USS Grunion (SS-216).

His Navy Commendation Medal Citation reads:

For meritorious conduct as a member of the crew of the U.S.S. GRUNION which destroyed three enemy destroyers while engaged in a war patrol in enemy controlled waters. Despite severe and persistent anti-submarine measures resulting from these three successful attacks, the GRUNION was brought safely through the counter attacks and continued an aggressive war patrol. As a member of the crew of the GRUNION, your performance of duty was an important and material contribution to the prosecution of this war.