MELBOURNE, Australia — Ian Kiernan, a record-breaking sailor whose encounters with pollution in the seas led him to found an organization dedicated to cleanup efforts around the world, died on Wednesday in Sydney, Australia. He was 78.

The cause was cancer, said Terrie-Ann Johnson, the managing director of Clean Up Australia, the organization Mr. Kiernan started with a group of friends in 1990.

In 1987, in a round-the-world yacht race, Mr. Kiernan set an Australian record for solo circumnavigation. It was during that race that he became aware of, and appalled by, the trash he saw in the Sargasso Sea, a region of the North Atlantic where four great currents converge.

“It is a place of mythology and mystery, a place I heard about as a child,” he told a newspaper later. But when he arrived, “the golden sea was absolutely choked with old thongs, plastic bags, garbage tins, empty toothpaste tubes and all that sort of thing.”