USS Thresher was the U.S. Navy submarine lost in 1963 during deep-diving trials off Massachusetts.
Thresher was a nuclear-powered attack submarine and the lead ship of its class. On 10 April 1963, it was conducting a deep-diving test about 220 miles east of Cape Cod when it suffered an emergency. The submarine could not regain depth and broke apart under pressure, killing all 129 people aboard, including sailors and civilian shipyard personnel.
A later investigation identified a combination of problems, including seawater entering the boat through a silver-brazed pipe joint and difficulty blowing water from the main ballast tanks. The tragedy led to the creation of the U.S. Navy’s SUBSAFE program, which introduced stricter controls over submarine design, construction, maintenance, and testing.
The wreck rests in several sections on the ocean floor. USS Scorpion, another U.S. nuclear submarine, was lost five years later, but it was a separate accident in the Atlantic Ocean.