"There was a call for people to go up on the boat deck," he said. "This is not a drill. The Japanese are here."
Kaup was 25 years old when he was on board the USS Medusa. He said he knew the world was changing.
"I was out in the machine shop and could feel the concussion of when the bombs went off," Kaup said.
Kaup said amid the confusion, his captain found clarity and dispatched crews to handle spies on shore, shoot down two planes and sink a submarine.
"The Medusa put a 3-inch shell through the conning tower of that sub," Kaup said.
Those actions saved countless lives.
The young-at-heart ex-sailor said he never imagined he'd be here to talk about the attack, just 10 days from his 100th birthday.
Kaup said he had a relative who lived to age 103, and his goal is to beat her and hit at least 104.