[Mr Quatro]

http://www.9websites.com/airforce/nucacc.htm

September 25, 1959
Whidbey Island, Washington

A U.S. Navy P-5M aircraft carrying an unarmed nuclear depth charge without its fissile core crashed into Puget Sound near Whidbey Island, Washington. The weapon was never recovered

Spring 1968
USS Scorpion (SSN-589)

Although the Pentagon has not publicly released details of the accident, it probably refers to the nuclear powered attack submarine USS Scorpion that was lost at sea. The sub, carrying unidentified nuclear weapons, was last heard from on May 21, 1968, while returning to Norfolk, Virginia, after a three month training exercise in the Mediterranean Sea. The USS Scorpion sank 400-500 miles southwest of the Azores.

Almost lost ...

November 10, 1970
USS Canopus (AS-34)

A fire broke out in the stern of the U.S. Navy submarine tender USS Canopus which was carrying several nuclear-armed missiles. The tender was at the Holy Loch submarine base in Scotland moored alongside two American nuclear-powered ballistic missile submarines. It took four hours to bring the fire under control.

April 9, 1981
USS George Washington (SSBN-598)

The nuclear-powered ballistic missile submarine USS George Washington collided with a Japanese freighter in the East China Sea, causing slight damage to the submarine's sail and sinking the freighter. The submarine carried up to 160 nuclear warheads on its 16 Poseidon C-3 sea-launched ballistic missiles.