Spence Dry was born on March 13, 1946, at the Navy Submarine Base in New London, Connecticut. He entered the U.S. Naval Academy on June 30, 1964, and was commissioned an Ensign on June 5, 1968. After attending the Naval Postgraduate School in Monterey, California, Dry was assigned to the destroyer USS Renshaw (DD-499) deploying with the ship on a WestPac cruise to Vietnam from June to December 1969. He reported to Basic Underwater Demolition/SEAL (BUD/S) training in Coronado in February 1970 and graduated with Class 56 in June 1970. Dry was then assigned to Underwater Demolition Team 13 (UDT-13), based at Coronado, where he deployed to the Philippines and then the Republic of Vietnam, where he worked with a SEAL Platoon in river reconnaissance, combat demolition, and search-and-destroy missions. LT Dry was reassigned to SEAL Team ONE in June 1971, and he became officer-in-charge of Alpha Platoon in April 1972. While in this position, he led Alpha Platoon during Operation Thunderhead, a clandestine mission to rescue escaping American Prisoners of War from North Vietnam. LT Dry was killed in action off the coast of North Vietnam on June 6, 1972, and was buried at Arlington National Cemetery. Spence Dry was the last Navy SEAL killed during the Vietnam War.

His 2nd Bronze Star with Valor Citation reads:

For heroic achievement in connection with combat operations against the enemy while serving as Officer-in-Charge of Alfa Platoon, SEAL Team ONE, during Operation Thunderhead from 1 April to 6 June 1972. While embarked aboard USS Grayback (LPSS 574), Lieutenant Dry conducted rigorous training evolutions in his relentless drive to increase his platoon's already high level of combat readiness. Demonstrating inspirational leadership and total mission commitment, he galvanized his platoon's morale prior to leading them in a combat mission off the coast of North Vietnam to rescue escaping United States Prisoners of War. Forced to abandon a swimmer delivery vehicle when its batteries were exhausted by heavy currents during a night reconnaissance mission on 3 June 1972, Lieutenant Dry rallied his men in enemy waters for eight hours. His decision to tow to sea and scuttle the inoperable vehicle prevented detection by the enemy and preserved operational security. Upon his rescue, while aboard USS Long Beach (CGN 9), Lieutenant Dry made a compelling argument to the on-scene tactical commander that it was essential he return to USS Grayback. Because his unique tactical information and superb leadership were judged vital to future SEAL insertions, he and his team were ordered to return to the submarine on 5 June 1972. His mission focus remained singular while leading the night mission and, despite the considerable risks, when given the signal that it was safe to exit the helicopter, Lieutenant Dry was the first to jump into the tumultuous waters. Under the arduous conditions, he was killed immediately upon impact. By his heroic leadership, courageous actions, and loyal devotion to duty, Lieutenant Dry reflected great credit upon himself and upheld the highest traditions of the United States Naval Service.

The combat distinguishing device is authorized.