In 1960, six submariners from USS Amberjack (SS-522) who had earned their dolphins were thrown overboard just as a destroyer passed nearby.

In accordance with Navy tradition, submariners are thrown over the side of their boats to commemorate special occasions such as qualifying for their submarine dolphin insignia or ending a war patrol with an advancement in rating.In 1960, six submariners from USS Amberjack (SS-522) who had earned their dolphins were thrown overboard just as a destroyer passed nearby. Unfamiliar with the tradition, the captain of the destroyer signaled “WHAT HAPPENED?” Amberjack responded “UNSHINED SHOES.”

On May 22, 1968, the American nuclear attack submarine USS Scorpion, went missing with 99 men aboard on her way back to Norfolk, Virginia.

Scorpion left New London, Connecticut, in February 1968 with a goal of reaching the Mediterranean Sea for a two-month European deployment, the Naval History and Heritage Command writes. However, they continue, she last radioed her position on May 21, 1968. She was lost southwest of the Azores, a group of islands about 950 miles west of mainland Portugal, on May 22, the US Navy reports.

Shortly after, being reported six days overdue in Norfolk, a search ensued, according to NHHC . On June 5, 1968, the submarine and its passengers were presumed lost, the Submarine Force Museum writes , joining the legion of US Navy submarines said to be on eternal patrol. However, the search continued. By October 1968, the crew of USNS Mizar had found Scorpion’s remains 10,000 feet below the surface of the Atlantic Ocean “using sonar, remote-control cameras and other instruments,” the Baltimore Sun reports.

According to declassified Navy documents, the probable cause of the the submarine’s demise was the deployment of one of its own torpedos, the Chicago Tribune reports . While the Navy declared evidence inconclusive, there has been pushback from veterans calling for an investigation as recently as 2012, USA Today reports . The 2012 request came after the Navy denied the proposal for an underwater excavation of the site by naval disaster experts, reporter Dan Vergano wrote .

The USS Thresher is the only other US submarine to be lost at sea since World War II ended, the National Interest ’s Kyle Mizokami writes.

A sextant from Scorpion is currently on display at the National Museum of the US Navy, located at the Washington Navy Yard.