6. Sinking of the USS Thresher USS Thresher was the lead boat of her class of nuclear-powered attack submarines in the United States Navy.
It was launched in 1960 and endured a series of tests through the Caribbean and along the Atlantic coast of the United States.
The first problem with the Thresher was in 1961 when she had to get a jump start from a World War II era, diesel-powered sub (the USS Cavalla). Plagued by mechanical injuries, the Thresher was eventually brought north for extensive overhauls.
On 9 April 1963 Thresher, now commanded by Lieutenant Commander John Wesley Harvey, got underway from Portsmouth at 8 am and rendezvoused with the submarine rescue ship Skylark at 11 am to begin its initial post-overhaul dive trials, in an area some 190 nmi (220 mi; 350 km) east of Cape Cod, Massachusetts.Days later, it was formally announced that all 129 passengers were considered deceased.