Last week, the Navy marked the 50th anniversary of the loss of the Skipjack-class nuclear submarine USS Scorpion (SSN 589) in a private observance at the Scorpion Memorial on Norfolk Naval Station. 99 officers and crew died when the submarine sank on May 22, 1968, over 400 miles southwest of the Azores in more than 10,000 feet of water. Exactly how and why the Scorpion sank remains a mystery.
After an extensive search, the wreckage of the submarine was located on Oct. 31, 1968, in more than 10,000 feet of water. Among the various hypotheses for why the submarine sank were a hydrogen explosion while charging batteries, the accidental activation or explosion of a torpedo, an attack by the Soviets, and even the malfunction of a trash disposal unit. A seven-panel naval board of inquiry concluded that “the certain cause of the loss of the Scorpion cannot be ascertained.”
The USS Scorpion is one of two nuclear submarines the U.S. Navy has lost, the other being USS Thresher. 1968 was a bad year for submarines. The USS Scorpion was one of four submarines that disappeared that year. The others were the others being the Israeli submarine INS Dakar, the French submarine Minerve and the Soviet submarine K-129.
diving to a depth greater than she was built for is the more likely scenario.
That would not be a complete answer as it does not give the reason for such a dive.
Listening to a friend who has served on nuclear subs an attack by a Russian vessel is highly plausible. He experienced just such an attack when they were on passage to the missile test ranges. No torpedo fired, because that would be an act of war, it tried to ram them and did cause some damage.