Prior to the attack, Casavant worked at Electric Boat Co. in Connecticut, building diesel submarines. He volunteered to serve on one of the boats in December 1941, despite the risks.
Casavant, 92, of Cocoa Beach, Fla., is among more than 20 World War II submarine veterans in town for Friday's annual ceremony at Naval Submarine Base Kings Bay to honor their dedicated service. The former electrician's mate said he had an all or nothing approach when he joined the Navy more than 70 years ago.
"If I came back from the war, I wanted to come back in one piece," he said.
Unfortunately, the reality of submarine service during World War II was that most sailors who served either made it home intact, physically at least, or they died.
Submarine service during World War II was the most dangerous duty in the military with casualty rates around 20 percent. More than 3,600 sailors -- nearly one in five serving aboard diesel submarines -- died during the war.
The submarine force was vital during the war, especially early on when the Pacific fleet was decimated by the attack at Pearl Harbor. The boats were the only threat to the Japanese fleet as it moved throughout the Pacific Ocean.
Though submarines only comprised 2 percent of the U.S. Navy, they were responsible for destroying 30 percent of the Japanese fleet during the war, including eight aircraft carriers, 11 cruisers and a battleship. They also destroyed 60 percent of the Japanese merchant fleet, cutting off crucial supplies to its military forces.
The success came at a heavy cost. During the war, 52 American subs were lost, all too often with no survivors ever found. In some instances, the reason a boat was lost at sea remains unknown.
Casavant served on two subs, the USS Norwhal and the USS Gabilan, during the war, completing nine patrols on both boats. Duty often meant staying submerged for extended periods on boats that, unlike modern subs, did not have the ability to produce oxygen.
Sometimes, the subs would have to remain submerged for extended periods to hide from a Japanese fleet or aircraft capable of dropping depth charges. The air got so thin at times, sailors were banned from smoking cigarettes, though the ban was merely procedural.
"When it said no smoking, you couldn't sneak one," he said.
In fact, they often wouldn't be able to smoke anyway because their lighters would not light in the oxygen-deprived atmosphere.
While they were on patrol, they had to dodge depth charges dropped from surface vessels and aircraft, as well as mines and torpedoes while seeking enemy vessels.
"We sunk a couple of ships," he said. "We got depth charges dropped on us but we got out of it."
The boats often patrolled with no escorts, meaning they had to improvise.
"If something broke down, you worked until it was fixed," he said.
During the final patrol of the war, Casavant was serving aboard the USS Gabilan when the crew rescued six men from two torpedo bombers and went into Tokyo Bay to rescue another three-man crew. A total of 17 aviators were rescued by the crew during their last patrol.
Casavant said the boat crossed the international dateline en route to Pearl Harbor when they got news of the Japanese surrender.
"We were all happy," he said.
He was discharged in December 1945 and reenlisted a month later after he was unable to find a job. He ended up retiring as a chief after a 30-year career in the Navy that included three Cold War deployments.