KITTERY — Family members of sailors killed in the deadliest submarine disaster in U.S. history are grateful for the sense of community surrounding a 55th anniversary commemoration.

The granddaughter of Charles Wiggins, one of the sailors who died on the USS Thresher, said it’s hard for others to understand the loss felt by those who were left behind, the Portsmouth Herald reported.

“We are fortunate today to be surrounded by people who understand,” Victoria Sallade said Saturday. “What we do here today is the best way to honor these men and to assure they are not forgotten.”

Hundreds of people, including current and retired sailors, in addition to descendants, attended a somber memorial Saturday at Traip Academy in Kittery.

Built at the Portsmouth Naval Shipyard in Kittery, the first-in-class Thresher was the world’s most advanced fast attack submarine when it was commissioned. But a malfunction during a deep-sea dive off Cape Cod on April 10, 1963 claimed the lives of all 129 aboard.

Mark Albert DiNola, son of Lt. Cmdr. Michael John DiNola, recalled being on the playground at Rye Elementary School in New Hampshire when he was sent home.

“I was at home when the men came to my house with the official news that he was gone. My father was a man of honor, courage and commitment. He is an American hero,” he said.

Capt. Oliver T. Lewis, commander of Submarine Squadron 12 based in Groton, Connecticut, talked about the loss, for the crew and the families left behind.

“This crew was sworn to protect and defend our country at the height of the Cold War, a critical time when the submarine force was at the forefront of the effort,” he said.

Lewis called Thresher “a constant symbol to safely operate and to guard against complacency, lest we be reminded by the power of the sea and loss of life.”

For the families, the silver lining is that subs are now safer.

After the disaster, the Navy accelerated safety improvements and created a program called “SUBSAFE,” an extensive series of design modifications, training and other improvements.