Eroni Kumana and his fellow islander Buiku Gasa were out in a canoe in 1943 when they came across the injured Kennedy, who was then a naval lieutenant, and members of his crew stranded on a coral atoll.
The pair helped the Americans survive and Kennedy went on to become the 35th president of the United States, keeping a coconut from the ordeal as a paperweight on his White House desk.
"It was very sad (but) he lived a full life and we are proud of him," he told AFP via telephone from the island, where villagers were preparing a feast in Kumana's honour.
Kennedy's boat PT-109 was on a night-time patrol when a Japanese destroyer suddenly loomed out of the dark and sheared the wooden vessel in half, according to the Smithsonian magazine.
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Spilled fuel ignited in the water, causing both the Japanese and other US PT boats to assume the 13-man crew had all perished in the shark-infested waters.
Kennedy, who had suffered a ruptured spinal disc, towed a badly burned crewman behind him during the marathon swim.
Eventually Kumana and Gasa passed in their canoe. They helped collect food for the crew and Kennedy sent them off to get help with a message etched into the shell of a coconut, reading: "Nauru Isl commander/native knows posit/he can pilot/11 alive/need small boat/Kennedy".
After being rescued, Kennedy retrieved the coconut and had it encased in plastic, using it as a paperweight throughout his post-war political career. It is still on display in the Kennedy Museum in Boston.
Kennedy was assassinated in 1963. Gasa died in November 2005.