Three years later, the Thresher was based in Connecticut and was performing routine drills when sea water began leaking into its engine room. The leak caused an electrical short and power outage that shut down the sub's reactor.
The Thresher's ballast tanks failed to blow, which would have forced the sub to surface. Instead, the ship imploded as it sank to the ocean floor at a depth of 8,400 feet.
Tom Shannon, of the U.S. Submarine Veterans' Marblehead Base, said the Thresher's sinking prompted stringent quality standards in the Navy meant to ensure the tragedy would never be repeated.
“Believe me, the history of the Thresher was not lost on any of us,” he said. “The sacrifice those men made was impressed upon all of us by our officers and senior members of our crews.”
Details were reported by The Daily News of Newburyport, Mass. Material from The Associated Press was used in this report.