America Never Expected Its ''Safest'' Sub to Kill 129 Men in Minutes on a Routine Test Dive

Discover how America's most advanced nuclear submarine became its deadliest loss—because of one cheap water pipe and a forgotten maintenance screen. April 10, 1963. USS Thresher, the Navy's pride, begins a routine test dive. Five minutes later, 129 men are dead at the bottom of the Atlantic. The disaster started with a water pipe joint that cracked under pressure at 1,300 feet. Seawater flooded the engine room, shutting down the nuclear reactor. The crew tried to surface by blowing ballast tanks—but maintenance crews had forgotten to remove temporary screens from the pipes nine months earlier. Ice clogged the screens. Air couldn't get through. The submarine kept sinking. At 2,400 feet, water pressure crushed the hull in 0.1 seconds. All 129 men died instantly. Their bodies remain sealed 8,400 feet underwater—America's largest underwater tomb. This disaster led to SUBSAFE, the most rigorous submarine safety program ever created. Every safety regulation for nuclear submarines today is written in the blood of the men who went down with Thresher.