Lin Mahner was born on June 30, 1943, in Chelsea Township, Wisconsin. He enlisted in the U.S. Navy on July 19, 1961, and completed basic training at NTC Great Lakes, Illinois, in October 1961. His first assignment was aboard the repair ship USS Vulcan (AR-5) from October 1961 to June 1962, followed by Hospital Corpsman School at NTC Great Lakes from June to October 1962. Petty Officer Mahner next attended the Field Medical Service School at MCB Camp Lejeune, North Carolina, from November to December 1962, and then served as a Hospital Corpsman with Marine Air Base Squadron 26 (MABS-26), of Marine Aircraft Group 26 (MAG-26) at Marine Corps Air Station New River, North Carolina, from December 1962 to March 1966. He attended additional medical training at Naval Station Washington, D.C., from April to October 1966, and with Naval Surface Force Atlantic from November to December 1966. Petty Officer Mahner next attended Underwater Swimmer School at Naval Base Key West, Florida, from December 1966 to February 1967, and then served with SEAL Team ONE at NAB Coronado, California, from March to August 1967. He deployed with SEAL Team ONE to South Vietnam from August 1967 to February 1968, and then returned with his Team to Coronado from February 1968 to February 1969. He deployed to Southeast Asia for a second time with SEAL Team ONE in February 1969, and served there until he was killed in action in South Vietnam on May 25, 1969. Lin Mahner was buried at the Whittlesey Catholic Cemetery in Whittlesey, Wisconsin.

His 1st Bronze Star Medal Citation reads:

For meritorious service in connection with operations against the enemy while serving in the Republic of Vietnam from 23 August 1967 to 23 February 1968. Petty Officer MAHNER distinguished himself as a member of a SEAL platoon in the Rung Sat Special Zone. He participated in over 35 combat operations. These operations ranged from combat patrols, both inland and on water, to search and destroy missions which brought Petty Officer MAHNER continuously under great danger and at times under enemy fire. While waiting in ambush on the night of 22 January 1968, Petty Officer MAHNER was made rear security. Just before dawn Petty Officer MAHNER alerted his squad of approaching Viet Cong. Although he did not take part in the direct action against the Viet Cong squad, his alertness and quick reaction resulted in the killing of two Viet Cong and averted possible friendly casualties. Petty Officer MAHNER's sense of responsibility, devotion to duty and exceptionally courageous behavior were in keeping with the highest traditions of the United States Naval Service.